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Title: Understanding Multi-Physics of Quench in "No-Insulation" Rare Earth Barium Copper Oxide Superconducting Magnets.
Creator: Bhattarai, Kabindra Ram, Hahn, Seung Yong, Pamidi, Sastry V., Larbalestier, D. (David), Kametani, Fumitake, Guo, Wei, Florida State University, FAMU-FSU College of Engineering ...
Show moreBhattarai, Kabindra Ram, Hahn, Seung Yong, Pamidi, Sastry V., Larbalestier, D. (David), Kametani, Fumitake, Guo, Wei, Florida State University, FAMU-FSU College of Engineering (Tallahassee, Fla.), Department of Mechanical Engineering
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Abstract/Description: Electromagnets are an important application of superconductivity as superconductors can provide large current density in the winding pack without any voltage drop or joule heating losses. High temperature superconducting (HTS) magnets have advantages over low temperature superconducting (LTS) magnets, particularly because HTS magnets have better stability and possibility of producing magnetic field higher than 20 T. However, protection of HTS magnets is challenging due to slow normal zone...
Show moreElectromagnets are an important application of superconductivity as superconductors can provide large current density in the winding pack without any voltage drop or joule heating losses. High temperature superconducting (HTS) magnets have advantages over low temperature superconducting (LTS) magnets, particularly because HTS magnets have better stability and possibility of producing magnetic field higher than 20 T. However, protection of HTS magnets is challenging due to slow normal zone propagation (NZP). When the NZP is slow, the stored magnetic energy is dissipated at localized area where the hot spot temperature can rise significantly and can cause "burn-out" damage on the superconductor. The no-insulation (NI) HTS winding technique has been experimentally demonstrated to be a promising technology, particularly to prevent a coil from electric burn-out, and has made it possible to reach a magnetic field of 45.5 T at the magnet center. NI magnets are dry wound and this adds to the ease in construction of NI coils as difficult epoxy impregnation process or wet winding process can be eliminated. The lack of insulation makes the magnet compact due to larger engineering current density, Je. Je of up to 1580 A/mm2 has been reported in NI coils, which is significantly larger than observed in insulated counterparts. The lack of low strength insulation also makes the magnet robust. NI winding using REBCO does not require processing steps such as epoxy impregnation or heat treatment, making its construction faster and convenient. However, as seen from the evidences of mechanical damage (seen from microscopy and critical current measurement) on the 45.5 T insert coil, there is a limit to this otherwise exciting technology. This research explores, in both simulation and experiment, the post-quench behaviors of NI magnets to quantitatively understand their self-protecting mechanism. NI quench modeling is challenging due to its non-linear, extremely fast and interrelated multiphysical behavior. A lumped circuit model combined with heat transfer and solid mechanics models is used to explain electrical, thermal, and mechanical responses in detail at the magnet level. In this model, each subcoil is modeled as single inductor (L 􀀀M) with variable resistances in series (Rq) and in parallel (Rc). For this purpose, some magnets that have been constructed and quenched at 4.2 K are being analyzed, which are 1) a stack of 3 double-pancake (DP) coils, 2) 14.5 T insert in 31 T resistive magnet, 3) 2 DP insert in 31 T resistive magnet, 4) 7 T standalone magnet, 5) 26 T standalone magnet, 6) 13 T HTS insert in 7 T background LTS magnet. The lessons learned from analysis of these magnets are presented in this work. The quench modeling allows us to look at temperature and stress in the magnet that are difficult to measure, but are important to make sure damages due to burn-out or overstraining do not occur during operation. With the lessons learned, this approach can now be used for future design of high field magnets to make sure mechanical damage during the magnet quench is prevented.
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Date Issued: 2019
Identifier: 2019_Summer_Bhattarai_fsu_0071E_15131
Format: Thesis

Title: Novel Applications of Sampling-Based Model Predictive Optimization.
Creator: Francis, Griffin Doran, Collins, E. (Emmanuel), Roberts, Rodney G., Clark, Jonathan E., Kumar, Rajan, Florida State University, FAMU-FSU College of Engineering, Department of...
Show moreFrancis, Griffin Doran, Collins, E. (Emmanuel), Roberts, Rodney G., Clark, Jonathan E., Kumar, Rajan, Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering
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Abstract/Description: This work presents two novel use cases to study domain applications of Sampling-Based Model Predictive Optimization (SBMPO). In the first case study, SBMPO is demonstrated to provide computationally efficient, direct generation of optimal trajectories for autonomous spacecraft rendezvous using time or distance cost functions. This effort addresses the challenges associated with the six degree-of-freedom relative motion planning problem presented by the rendezvous scenario. Additionally,...
Show moreThis work presents two novel use cases to study domain applications of Sampling-Based Model Predictive Optimization (SBMPO). In the first case study, SBMPO is demonstrated to provide computationally efficient, direct generation of optimal trajectories for autonomous spacecraft rendezvous using time or distance cost functions. This effort addresses the challenges associated with the six degree-of-freedom relative motion planning problem presented by the rendezvous scenario. Additionally, various modifications to the fundamental SBMPO algorithm are developed to accommodate the domain-specific constraints associated with the orbital navigation. In the second study, SBMPO is applied to the resource allocation problem associated with cost-based scheduling of distributed energy resources in a microgrid. Unlike the spacecraft trajectory planning scenario, the resource allocation task is characteristic of a more generalized optimal control problem. In any case, SBMPO is applied within the Advanced Optimal Resource Allocation (AORA) dispatch control scheme to achieve cost-optimal sequencing of power resources to deliver a predicted load.
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Date Issued: 2019
Identifier: 2019_Spring_Francis_fsu_0071E_15029
Format: Thesis

Title: Manufacturing of Multimaterial Composites via Dual Robotic 3D Printing.
Creator: Frketic, Jolie Breaux, Dickens, Tarik, Clark, Jonathan E., Ramakrishnan, Subramanian, Liang, Zhiyong (Richard), Wang, Hui, Florida State University, FAMU-FSU College of...
Show moreFrketic, Jolie Breaux, Dickens, Tarik, Clark, Jonathan E., Ramakrishnan, Subramanian, Liang, Zhiyong (Richard), Wang, Hui, Florida State University, FAMU-FSU College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: Composite additive manufacturing (AM) is able to create products that have never before been able to be made. However, several processing and material setbacks keep AM from becoming the all-encompassing methodology for multifunctional printed composite parts. Current AM methods to create composites are focused on printing single materials, and while able to create complex parts quickly, have yet to leverage their full capability. To make strides towards an all-encompassing multi-material...
Show moreComposite additive manufacturing (AM) is able to create products that have never before been able to be made. However, several processing and material setbacks keep AM from becoming the all-encompassing methodology for multifunctional printed composite parts. Current AM methods to create composites are focused on printing single materials, and while able to create complex parts quickly, have yet to leverage their full capability. To make strides towards an all-encompassing multi-material additive manufacturing system, a collaborative dual selective compliance assembly robotic arm manufacturing system has been developed for cooperative additive manufacturing (CO-AM). The inclusion of cooperative robotic systems working simultaneously on a part while near each other spurs inquiry to the issues of effectiveness and practicality compared to what is witnessed in conventional operation. This research highlights our work on fundamentally understanding the process control-structure-property relationships of a novel mechatronic system for additive processing. The first study aims to narrate the design process and capabilities of this cooperative system, as well as measure current performance under typical operation. Investigations were aided with (1) computer vision analysis and (2) dynamic modeling to provide insight into the limitations of the current system. This study seeks to benchmark the performance of CO-AM as it compares to modern on market systems. The study shows that the CO-AM system can reach the same resolution as typical extrusion manufacturing devices. A time study found that a 36% reduction in time is able to be achieved in a non-optimized part, yielding an advantage over typical systems. A second study investigates the processing parameters (road overlap, speed, the time between extrusions, stepping and nozzle size) in CO-AM and how these process-property relationships can be used to create the strongest weld in the seam between two halves of a part printed collaboratively. From this study, it was found that the speed of printing, print overlap, and nozzle size were the most important in having a stronger weld. From these results, design rules and processing parameters for thermoplastic CO-AM were developed. Finally, a study was conducted to investigate the polymer welding and adhesion between adjoining printed roads. Theoretical studies have been used to determine how polymer-polymer welding at the interface between adjacent roads affects the strength between these printed interfaces. Micrographs of printed compact tension specimen interfaces were analyzed for thermoplastic welding. An image segmentation program was developed to elucidate the polymer diffusion and adhesion of printed parts and describes the strength of the printed part. It was found that a coefficient for weld entanglement is able to accurately depict the strength of a printed thermoplastic when an assumed strength along the weld is considered to be around 25% of the full strength of an injection molded part. This helps in further studies by enhancing the knowledge of the process-property relationship that is created when using additive manufacturing.
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Date Issued: 2019
Identifier: 2019_Spring_Frketic_fsu_0071E_14912
Format: Thesis

Title: Characterization of a High-Lift, Supercritical Airfoil with Microjets.
Creator: Aley, Kade Stephen, Kumar, Rajan, Oates, William, Shoele, Kourosh, Florida State University, FAMU-FSU College of Engineering (Tallahassee, Fla.), Department of Mechanical...
Show moreAley, Kade Stephen, Kumar, Rajan, Oates, William, Shoele, Kourosh, Florida State University, FAMU-FSU College of Engineering (Tallahassee, Fla.), Department of Mechanical Engineering
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Abstract/Description: Active flow control (AFC) has the potential for substantial performance gains and meeting the challenges of next-generation high-lift aircraft. High-lift wings employ multi-element trailing edge flaps during takeoff and landing. When the aircraft is at cruise speed, these flaps are not required and are retracted to reduce drag. These aircraft wings with high-lift mechanisms enhance the lift characteristics at slower speeds, but suffer due to the added weight of these deployment/retraction...
Show moreActive flow control (AFC) has the potential for substantial performance gains and meeting the challenges of next-generation high-lift aircraft. High-lift wings employ multi-element trailing edge flaps during takeoff and landing. When the aircraft is at cruise speed, these flaps are not required and are retracted to reduce drag. These aircraft wings with high-lift mechanisms enhance the lift characteristics at slower speeds, but suffer due to the added weight of these deployment/retraction mechanisms. In the present study, we have investigated the effect of active flow control using microjets to enhance the performance of a two-dimensional high-lift supercritical airfoil with a simply hinged flap. The airfoil used in the study is the NASA Energy Efficient Transport (EET) and the wind-tunnel tests were conducted at a freestream velocity of 20 m/s. Two different scaled models were used corresponding to Reynolds numbers of 1.3 x 105 and 3.4 x 105. The experiments pertaining to the small scaled model were carried out with two angles of incidence of 0° and 4° at a constant flap deflection of 20°. For the large scale model, a constant angle of incidence of 0° and flap deflection angles of 20° and 30° were investigated. A range of microjet momentum ratios and microjet orientations were studied for both models. Particle Image Velocimetry was carried out to study the mean velocity field and the effect of microjet control at the flap region of the airfoil. For the first model, the baseline flow at both the angles of incidence separates at the hinge line and remain separated over the entire flap region. The size of the re-circulation region is found to gradually decrease with an increase in microjet momentum ratio. Microjets oriented normal to the airfoil surface were relatively more effective and successful in re-attaching the flow over the entire airfoil at both the angles of incidence. Experiments for the second model consisted of both Planar and Stereoscopic Particle Image Velocimetry. The baseline flow is separated over a third of the flap at 20° and over the entire flap at 30°. Microjets oriented at a more tangential angle are able to completely re-attach the flow at both flap angles. In general, active flow control using high-momentum microjets was very effective in eliminating/reducing flow separation, however, its effectiveness was dependent on the geometric and flow parameters.
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Date Issued: 2019
Identifier: 2019_Summer_Aley_fsu_0071N_15353
Format: Thesis

Title: Towards Terrain-Adaptive Feedback Control for Legged Locomotion via Understanding of Dynamic Interaction with Uncertain Rough Terrains.
Creator: Gao, Wei, Clark, Jonathan E., Roberts, Rodney G., Oates, William, Hollis, Patrick J., Florida State University, FAMU-FSU College of Engineering (Tallahassee, Fla.), Department...
Show moreGao, Wei, Clark, Jonathan E., Roberts, Rodney G., Oates, William, Hollis, Patrick J., Florida State University, FAMU-FSU College of Engineering (Tallahassee, Fla.), Department of Mechanical Engineering
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Abstract/Description: Legged locomotion is advantageous on difficult natural terrains due to it only requiring discrete ground contacts. Biological systems with limbs have developed multiple levels of control to afford such fast and robust legged locomotion. Similarly, bio-inspired controls on legged robots can also be divided into equivalent levels. The high-level controllers, including the brain and the reflex level controllers, process the environmental information and communicate with muscles that are denoted...
Show moreLegged locomotion is advantageous on difficult natural terrains due to it only requiring discrete ground contacts. Biological systems with limbs have developed multiple levels of control to afford such fast and robust legged locomotion. Similarly, bio-inspired controls on legged robots can also be divided into equivalent levels. The high-level controllers, including the brain and the reflex level controllers, process the environmental information and communicate with muscles that are denoted as low-level controllers, or the preflex level controllers. The low-level controllers then directly contribute to dynamics of the legs. Currently, various low-level controllers have been developed and shown to have the capability of overcoming rough but certain terrains, i.e. terrains with height variation but are infinitely hard. However, uncertain rough terrains universally exist in the natural world. To traverse such terrains, the high-level controllers need to estimate terrain characteristics and adjust the low-level controllers to accommodate the terrain changes as the robots are operating. This dissertation provides the necessary techniques to create a feedback control routine to accomplish such high-level tasks and achieve terrain-adaptive legged locomotion. It starts from studying the effect of leg stiffness and damping on locomotion performance, which necessitates careful leg design for successful legged locomotion and advanced low-level leg controllers for improved performance. The direct collocation method is then introduced to optimize spring modulation trajectories as an advanced leg controller. However, the power of the optimization results cannot be sufficiently exploited unless terrain characteristics are known beforehand. As a result, the Maximum Entropy method is developed to estimate terrain characteristics using data from sensors onboard. This method allows fusion of data from heterogeneous sources to obtain objective uncertainty quantification of terrain characteristics. With the statistical information about terrain characteristics from the Maximum Entropy method, the routine can finally update the low-level leg controller such that the robots can survive traversing uncertain rough terrains.
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Date Issued: 2019
Identifier: 2019_Summer_Gao_fsu_0071E_15365
Format: Thesis

Title: The Development of Inhomogeneous Microstructures during 3-Axis Forging.
Creator: Carnrike, Talya Rachel, Kalu, Peter N., Tawfiq, Kamal Sulaiman, Hruda, Simone Peterson, Moore, Carl A., Florida State University, FAMU-FSU College of Engineering, Department of...
Show moreCarnrike, Talya Rachel, Kalu, Peter N., Tawfiq, Kamal Sulaiman, Hruda, Simone Peterson, Moore, Carl A., Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering
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Abstract/Description: Severe plastic deformation, especially 3-Axis Forging (3AF), has been used in several industries as a production method for various tools and equipment. Components or items produced by this method are characterized by inhomogeneous microstructures. A prior study done in this laboratory using 3AF on Cu and Nb materials revealed the presence of microstructural inhomogeneities upon the first cycle of processing. In this study, finite element method (Deform) was used to investigate the nature of...
Show moreSevere plastic deformation, especially 3-Axis Forging (3AF), has been used in several industries as a production method for various tools and equipment. Components or items produced by this method are characterized by inhomogeneous microstructures. A prior study done in this laboratory using 3AF on Cu and Nb materials revealed the presence of microstructural inhomogeneities upon the first cycle of processing. In this study, finite element method (Deform) was used to investigate the nature of the development of microstructural inhomogeneity when materials are subjected to 3AF. Analysis of the strain distribution patterns was carried out for uniaxial compression, 1 cycle and 2 cycles of 3AF subjected to three different primary displacement rates (2.54, 25.4, and 254 mm/s) and various friction factors (0, 0.08, 0.12, 0.25, 0.3, 0.4, 0.7, and 0.8). The study was confined to the first two cycles because the majority of grain refinement occurred in this region. Particular attention was paid to the friction factor, m, which is a function of the type of lubricant used during deformation. The results show that using lubricants with higher friction factor increased the strain range (difference between maximum and minimum effective strain), thus the degree of inhomogeneity during deformation. A critical friction factor, mc, was found to exist above which an inhomogeneous microstructure emerges. Analysis of the strain parameters revealed that there is a logarithmic relationship, y = a ln(x) + b, between the strain range, maximum effective strain and/or minimum effective strain, y, and the displacement rate, x. It is important to note that a and b are material constants. Niobium, Nb, was characterized by a higher strain range in all forms of deformation when compared to Cu. Flownet maps constructed for the deformation processes for friction factor m > mc revealed the existence of four major zones. Zone A (core), which corresponds to the maximum strain was found in the regions not affected by friction between the sample and compression plates. Zone C had the lowest strain due to its contact with the compression plates thereby restricted by friction. However, zones (B and D) exhibited medium to low strain as they are affected by friction but not to the degree of zone C. The flownet maps were found to correlate well with the experimental hardness data of the materials. The study clearly shows that the microstructural inhomogeneity developed during 3AF depends very much on the lubricant type used.
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Date Issued: 2019
Identifier: 2019_Fall_Carnrike_fsu_0071E_15479
Format: Thesis

Title: Flow Physics and Nonlinear Dynamics of Separated Flows Subject to ZNMF-Based Control.
Creator: Deem, Eric Anthony, Cattafesta, Louis N., Sussman, Mark, Taira, Kunihiko, Collins, E., Moore, Matthew Nicholas J., Hemati, Maziar, Florida State University, College of...
Show moreDeem, Eric Anthony, Cattafesta, Louis N., Sussman, Mark, Taira, Kunihiko, Collins, E., Moore, Matthew Nicholas J., Hemati, Maziar, Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: Aircraft, turbomachinery, wind turbines, and other systems that generate or rely on aerodynamic forces are designed to operate most efficiently when flows are fully attached. However, especially due to increasing off-design performance requirements, there is significant risk of inefficient operation or failure due to flow separation. This work formulates a procedure for extending the performance envelope of many fluidic systems by delaying flow separation through real time separated flow...
Show moreAircraft, turbomachinery, wind turbines, and other systems that generate or rely on aerodynamic forces are designed to operate most efficiently when flows are fully attached. However, especially due to increasing off-design performance requirements, there is significant risk of inefficient operation or failure due to flow separation. This work formulates a procedure for extending the performance envelope of many fluidic systems by delaying flow separation through real time separated flow state estimation and control. The history of active separation control is rich; however the approach presented here is novel in that it employs "real time" dynamical system updates to track nonlinear variations in the flow and provide robustness to flow state conditions. First, the dynamics of the canonical laminar separated flow over a flat plate at Rec=10⁵ are characterized by employing full-field, time-resolved PIV and unsteady surface pressure measurements. Dynamic Mode Decomposition (DMD) is employed on the high dimensional PIV velocity fields to identify the dynamically relevant spatial structure and temporal characteristics of the separated flow. Then, results of various cases of open-loop control using a zero-net mass flux actuator slot located just upstream of separation are presented that show separation reduction occurs for the employed actuation method. Real time estimates of the dynamical characteristics are provided by performing online DMD on measurements from a linear array of unsteady surface pressure transducers. The results show that online DMD of the pressure measurements provides reliable estimates of the modal characteristics of the separated flow subject to forcing. Furthermore, the dynamical estimates are updated at a rate commensurate with the characteristic time scales of the flow. Therefore, as the separated flow reacts to the applied forcing, online DMD applied to the surface pressure measurements provides a time-varying linear estimate of the evolution of the flow. Building upon these results, methods for adaptive control of flow separation based on the model provided by online DMD are formulated and implemented on the separated flow. Feedback control is implemented in which Linear Quadratic Regulator gains are computed recursively as the model provided by online DMD is updated. This physics-motivated, autonomous approach results in more efficient flow reattachment, requiring approximately 30% less actuator effort as compared with the commensurate open loop forcing case. Since this approach relies solely on observations of the separated flow, it is robust to variable flow conditions. Additionally, this approach does not require prior knowledge of the characteristics of the separated flow.
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Date Issued: 2018
Identifier: 2018_Su_Deem_fsu_0071E_14530
Format: Thesis

Title: Network-Theoretic and Data-Based Analysis and Control of Unsteady Fluid Flows.
Creator: Nair, Aditya Gopimohan, Taira, Kunihiko, Sussman, Mark, Cattafesta, Louis N., Oates, William, Alvi, Farrukh S., Brunton, Steven L. (Steven Lee), Florida State University,...
Show moreNair, Aditya Gopimohan, Taira, Kunihiko, Sussman, Mark, Cattafesta, Louis N., Oates, William, Alvi, Farrukh S., Brunton, Steven L. (Steven Lee), Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: Unsteady fluid flows have complex dynamics due to the nonlinear interactions amongst vortical elements. In this thesis, a network-theoretic framework is developed to describe vortical and modal (coherent structure) interactions in unsteady fluid flows. A sparsified-dynamics model and a networked-oscillator model describe the complex dynamics in fluid flows in terms of vortical and modal networks, respectively. Based on the characterized network interactions, model-based feedback control laws...
Show moreUnsteady fluid flows have complex dynamics due to the nonlinear interactions amongst vortical elements. In this thesis, a network-theoretic framework is developed to describe vortical and modal (coherent structure) interactions in unsteady fluid flows. A sparsified-dynamics model and a networked-oscillator model describe the complex dynamics in fluid flows in terms of vortical and modal networks, respectively. Based on the characterized network interactions, model-based feedback control laws are established, particularly for controlling the flow unsteadiness. Furthermore, to characterize model-free feedback control laws for suppressing flow separation in turbulent flows, a data-driven approach leveraging unsupervised clustering is developed. This approach alters the Markov transition dynamics of fluid flow trajectories in an optimal manner using a cluster-based control strategy. To describe vortical interactions, dense fluid flow graphs are constructed using discrete point vortices as nodes and induced velocity as edge weights. Sparsification techniques are then employed on these graph representations based on spectral graph theory to construct sparse graphs of the overall vortical interactions which maintain similar spectral properties as the original setup. Utilizing the sparse vortical graphs, a sparsified-dynamics model is developed which drastically reduces the computational cost to predict the dynamical behavior of vortices, sharing characteristics of reduced-order models. The model retains the nonlinearity of the interactions and also conserves the invariants of discrete vortex dynamics. The network structure of vortical interactions in two-dimensional incompressible homogeneous turbulence is then characterized. The strength distribution of the turbulence network reveals an underlying scale-free structure that describes how vortical structures are interconnected. Strong vortices serve as network hubs with smaller and weaker eddies predominantly influenced by the neighboring hubs. The time evolution of the fluid flow network informs us that the scale-free property is sustained until dissipation overtakes the flow physics. The types of perturbations that turbulence network is resilient against is also examined. To describe modal interactions in fluid flows, a networked-oscillator-based analysis is performed. The analysis examines and controls the transfer of kinetic energy for periodic bluff body flows. The dynamics of energy fluctuations in the flow field are described by a set of oscillators defined by conjugate pairs of spatial POD modes. To extract the network of interactions among oscillators, impulse responses of the oscillators to amplitude and phase perturbations are tracked. Using linear regression techniques, a networked oscillator model is constructed that reveals energy exchanges among the modes. In particular, a large collection of system responses are aggregated to capture the general network structure of oscillator interactions. The present networked oscillator model describes the modal perturbation dynamics more accurately than the empirical Galerkin reduced-order model. The linear network model for nonlinear dynamics is subsequently utilized to design a model-based feedback controller. The controller suppresses the modal fluctuations and amplitudes that result in wake unsteadiness leading to drag reduction. The strength of the approach is demonstrated for a canonical example of two-dimensional unsteady flow over a circular cylinder. The network-based formulation enables the characterization and control of modal interactions to control fundamental energy transfers in unsteady bluff body flows. Finally, unsupervised clustering and data-driven optimization of coarse-grained control laws is leveraged to manipulate post-stall separated flows. Optimized feedback control laws are deduced in high-fidelity simulations in an automated, model-free manner. The approach partitions the baseline flow trajectories into clusters, which corresponds to a characteristic coarse-grained phase in a low-dimensional feature space constituted by feature variables (sensor measurements). The feedback control law is then sought for each and every cluster state which is iteratively evaluated and optimized to minimize aerodynamic power and actuation power input. The control optimally transforms the Markov transition network associated with the baseline trajectories to achieve desired performance objectives. The approach is applied to two and three-dimensional separated flows over a NACA 0012 airfoil at an angle of attack of 9° Reynolds number Re = 23000 and free-stream Mach number M∞ = 0.3. The optimized control law minimizes power consumption for flight enabling flow to reach a low-drag state. The analysis provides insights for feedback flow control of complex systems characterizing global cluster-based control laws based on a data-driven, low-dimensional characterization of fluid flow trajectories. In summary, this thesis develops a novel network-theoretic and data-based framework for analyzing and controlling fluid flows. The framework incorporates advanced mathematical principles from network science, graph theory and dynamical systems to extract fundamental interactions in fluid flows. On manipulating these interactions, wake unsteadiness in bluff body flow is reduced leading to drag reduction. Finally, data-based methods are developed to deduce optimal feedback control laws for post-stall separated flows. The network-theoretic and data-based approaches provides insights on fundamental interactions in fluid flows which paves the way for design of novel flow control strategies.
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Date Issued: 2018
Identifier: 2018_Su_Nair_fsu_0071E_14745
Format: Thesis

Title: Enhancing Polymer Composites with Triboluminescent Materials.
Creator: Scheiner, Margaret Victoria, Okoli, Okenwa O. I., Sobanjo, John Olusegun, Ma, Biwu, Yu, Zhibin, Dickens, Tarik, Florida State University, FAMU-FSU College of Engineering,...
Show moreScheiner, Margaret Victoria, Okoli, Okenwa O. I., Sobanjo, John Olusegun, Ma, Biwu, Yu, Zhibin, Dickens, Tarik, Florida State University, FAMU-FSU College of Engineering, Department of Industrial and Manufacturing Engineering
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Abstract/Description: Fiber-reinforced polymer composites (FRPCs) have a variety of applications in diverse industries. However, predicting the failure of FRPCs is more difficult than predicting the failure of more traditional materials like steel. Furthermore, composites can suffer extreme internal damage, but show little if any external indication that damage has occurred. This study investigated the potential for integrated structural health monitoring and self-healing for polymer composites utilizing...
Show moreFiber-reinforced polymer composites (FRPCs) have a variety of applications in diverse industries. However, predicting the failure of FRPCs is more difficult than predicting the failure of more traditional materials like steel. Furthermore, composites can suffer extreme internal damage, but show little if any external indication that damage has occurred. This study investigated the potential for integrated structural health monitoring and self-healing for polymer composites utilizing triboluminescent (TL) materials. This study followed three phases. In Phase 1, the effects of enhancing resins with TL zinc sulfide manganese (ZnS:Mn) and europium dibenzoylmethide triethylamine (EuD4TEA) phosphors were investigated, including optimization of the EuD4TEA synthesis process and development of a model for tensile modulus based on TL inclusion and type of resin. EuD4TEA should be synthesized using at minimum 80 mmol/L europium nitrate and 260 mmol/L DBM, with at least 80 mmol/L TEA. ZnS:Mn was observed to increase elastic modulus of vinyl ester and light-curable polyurethane, by 103% and 60%, respectively. The larger EuD4TEA crystals decreased vinyl ester’s (VE’s) elastic modulus by 11%, at least partly due to particle size. EuD4TEA-enhanced light-curing polyurethane suffered a 95% decrease in elastic modulus, mostly due to incomplete cure. Inclusion of EuD4TEA in the VE resin resulted in the formation of voids, approximately the size of the EuD4TEA crystals. Protecting the EuD4TEA crystals from the heat of cure reduced the formation of bubbles, and improved TL emissions. Thermogravimetric analysis indicated the NHEt3 group was lost as EuD4TEA was heated above 100 °C. In Phase 2, a new measurement system was developed to evaluate luminescence and longevity of TL-enhanced resins. Optical fibers with a tip coating of TL-enhanced resin both provided a stage for the sample and directed the TL emissions into a light sensor. This tip-coated optical fiber method results in less variation in TL signal for ZnS:Mn-enhanced VE and sucrose-enhanced VE samples than impacts on loose ZnS:Mn and sucrose crystals. The intensity of TL emissions may be increased sevenfold by exposing the TL-enhanced sample to ultraviolet light immediately prior to TL testing. In Phase 3, the potential for TL-induced polymerization (and, by extension, TL-induced healing) was assessed. The results show polymers may be cured with visible light, even low-intensity photoluminescence, indicating feasibility of TL-induced healing.
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Date Issued: 2018
Identifier: 2018_Sp_Scheiner_fsu_0071E_14378
Format: Thesis

Title: Experimental Characterization and Uncertainty Quantification of High Temperature Pressure Sensing Materials.
Creator: Consoliver-Zack, Jakob, Oates, William, Hellstrom, Eric, Kumar, Rajan, Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: Sapphire is presently being utilized in optical based pressure traducers for use in measuring pressure at high temperatures. The robustness of sapphire makes it an ideal material for use as a high temperature sensor; however, not without its own challenges. Sapphire cannot be machined using conventional methods so alternatives such as laser machining us- ing a picosecond laser have been investigated. This method has shown to cause significant changes to the material including modulus,...
Show moreSapphire is presently being utilized in optical based pressure traducers for use in measuring pressure at high temperatures. The robustness of sapphire makes it an ideal material for use as a high temperature sensor; however, not without its own challenges. Sapphire cannot be machined using conventional methods so alternatives such as laser machining us- ing a picosecond laser have been investigated. This method has shown to cause significant changes to the material including modulus, strength, and toughness. The specific cause of these changes is hypothesized to be due to residual stress induced in the crystal lattice. This was investigated using x-ray diffraction coupled with Bayesian uncertainty techniques. The computed tensor showed in-plane compressive stresses which would result in increased strength. Due to the challenges of machining sapphire, an alternative material called Maxthal 211 (Ti2AlC) was also investigated. The mechanical response under cyclic loading both pre and post annealing was examined using a uniaxial wafer bending setup. Hysteretic losses were shown to drop significantly on the second cycle, regardless of the annealing treatment.
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Date Issued: 2018
Identifier: 2018_Su_ConsoliverZack_fsu_0071N_14620
Format: Thesis

Title: Thrust Measurements on a Rocket Nozzle Using Flow-Field Diagnostics.
Creator: Vemula, Rohit Chandra, Kumar, Rajan, Oates, William, Yaghoobian, Neda, Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: With an increase in the number of space transport applications, the need for larger, more powerful and efficient rocket motors are the need of the day. Thus, optimizing the thrust generated by these rocket motors is of great importance, which can be achieved by bell-shaped nozzles with high area ratios. However, the high area ratios result in significant over-expansion at sea level conditions, that cause flow separation inside the nozzle and generate side-loads. Several novel nozzle designs...
Show moreWith an increase in the number of space transport applications, the need for larger, more powerful and efficient rocket motors are the need of the day. Thus, optimizing the thrust generated by these rocket motors is of great importance, which can be achieved by bell-shaped nozzles with high area ratios. However, the high area ratios result in significant over-expansion at sea level conditions, that cause flow separation inside the nozzle and generate side-loads. Several novel nozzle designs are being developed to overcome the flow separation phenomenon. Characterizing the thrust output from these nozzles in a laboratory is vital for their successful development and implementation. Conventionally, the thrust from a nozzle is measured using load cells on a thrust stand. A thrust stand can provide limited information on the loads generated by the flow through a nozzle, such as the magnitude and direction of time average loads, but the flow features responsible for generating them remain elusive. In the present study, a novel method to estimate thrust from flow-field data, obtained by Particle Image Velocimetry (PIV) experiments and Pitot pressure survey at the nozzle exit, is proposed. The thrust estimated by this method is then validated with the conventional thrust measurements using load cells. A Mach 4 convergent-divergent nozzle with 12.7 mm throat diameter was tested using compressed air at a range of substantially over-expanded operating conditions with Nozzle pressure ratio (NPR) of 4, 5, 6, 7 and 7.5, at two temperature ratios (TR =1.2 and TR =1.5). The flow field at the nozzle exit was surveyed at these conditions using a Pitot tube mounted on a 2-D traverse system and the stereo PIV technique. Using the data obtained from both the flow surveys in the rocket thrust equation, the values of thrust are estimated. The thrust estimated from the flow field data showed identical levels at both temperature ratios. This suggested that temperature ratio has a negligible impact on the thrust measured at respective NPR. Using a load cell, the thrust produced by the nozzle was measured for each NPR at isothermal condition (TR=1). A comparison between the thrust obtained by the two methods verified that PIV and pressure surveys could be used to determine the time-averaged thrust of a nozzle to within 6% of the load cell readings. This experimental study provides a reliable alternative method for rocket nozzle thrust measurements
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Date Issued: 2018
Identifier: 2018_Sp_Vemula_fsu_0071N_14314
Format: Thesis

Title: Multiscale Modeling with Applications to High Temperature Pressure Sensing.
Creator: Woerner, Peter Christopher, Oates, William, Gallivan, Kyle A., Taira, Kunihiko, Lin, Shangchao, Mendoza-Cortes, Jose L., Florida State University, FAMU-FSU College of...
Show moreWoerner, Peter Christopher, Oates, William, Gallivan, Kyle A., Taira, Kunihiko, Lin, Shangchao, Mendoza-Cortes, Jose L., Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering
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Abstract/Description: Computational material modeling has a history supporting of engineering applications. This dissertation presents two focal areas of research. The first is modeling and characterizing ultrafast laser machining of sapphire. A three dimensional model of laser machining is presented as an extension to a previously published one dimensional model. The bulk of the work focuses on finite element modeling of nanoindetation of laser machined and pristine sapphire specimen in order to quantify material...
Show moreComputational material modeling has a history supporting of engineering applications. This dissertation presents two focal areas of research. The first is modeling and characterizing ultrafast laser machining of sapphire. A three dimensional model of laser machining is presented as an extension to a previously published one dimensional model. The bulk of the work focuses on finite element modeling of nanoindetation of laser machined and pristine sapphire specimen in order to quantify material differences due to laser machining. Discussions on generalized plasticity and finite element modeling are including before presenting results, As the second focal point, this dissertation presents applications of network theory to atomistic material models. A novel method of representing materials as weighted graphs is developed. We believe this approach extends the use of networks beyond their traditional use in chemistry. Within the weighted network approach we show that spectral sparsification is an excellent tool that reduces complex force interactions while maintaining minimal errors. The results are shown to be particularly useful for approximating long range potentials. We also present preliminary work which suggest the network based approach may be suitable for detecting defects and developing macroscale consitutive laws.
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Date Issued: 2018
Identifier: 2018_Fall_Woerner_fsu_0071E_14880
Format: Thesis

Title: Mechanical Properties of Superpower and Sunam Rebco Coated Conductors.
Creator: Radcliff, Kyle, Hahn, Seung Yong, Larbalestier, D., Cooley, L., Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering
Abstract/Description: High Temperature superconductors (HTS) are the only way to achieve elds with superconducting magnets higher than the 25 T of Low Temperature Superconductors (LTS). No-Insulation (NI) REBCO magnets using REBa2Cu3Ox as the superconductor require less copper stabilizer than insulated magnets and thin (30 m) substrates have now become available. In our recent small coil attack on elds greater than 40 T, we have seen that overstrain damage can easily occur even at frequently used design strain of...
Show moreHigh Temperature superconductors (HTS) are the only way to achieve elds with superconducting magnets higher than the 25 T of Low Temperature Superconductors (LTS). No-Insulation (NI) REBCO magnets using REBa2Cu3Ox as the superconductor require less copper stabilizer than insulated magnets and thin (30 m) substrates have now become available. In our recent small coil attack on elds greater than 40 T, we have seen that overstrain damage can easily occur even at frequently used design strain of 0.4%. Here we present an experimental study of the uniaxial stress () characteristics of SuperPower and SuNAM coated conductors and also do strain-critical current (Ic()) measurements to nd the onset of permanent damage to Ic. We found considerable variability in their 77 K mechanical properties. The cold-rolled Hastelloy C-276 substrate of the SuperPower is much stronger than the cold-rolled 310 stainless steel substrate used by SuNAM, but of more concern is the variability of the strength of dierent batches of SuNAM tape. Mechanical variability in the dierent SuNAM batches creates a challenge when designing for magnets. We also examined the eects of strain on critical current performance, nding that the critical current of the SuNAM conductor becomes irreversible over a wide range of strains from 0.3-0.6%. Suspecting that some annealing of the substrates occurs during REBCO deposition in the vicinity of 750 C, we performed short heat treatments at 700, 750, and 800 C of samples of the as-delivered substrates used by manufacturers. We found that there was little change to strength of the Hastelloy used by SuperPower but substantial change to the 310 stainless steel used by SuNAM. Our results show that any high eld operation at strains of 0.4% or more requires detailed knowledge of the mechanical properties of the tapes being used, especially for magnets using SuNAM tapes with cold-rolled 310 stainless steel substrates.
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Date Issued: 2018
Identifier: 2018_Fall_Radcliff_fsu_0071N_14949
Format: Thesis

Title: Flowfield of a Three-Dimensional Swept-Shock Boundary Layer Interaction at Mach 2.
Creator: Arora, Nishul, Alvi, Farrukh S., Okoli, Okenwa O. I., Kumar, Rajan, Collins, E., Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering
Abstract/Description: An experimental study is conducted on the interaction of a swept-shock wave with a turbulent boundary layer. The shock wave is generated by a sharp un-swept fin in a Mach 2 flow, where the strength of the interaction is varied from weak to moderate by changing the fin angle of attack from 10° to 15°, which corresponds to a normal Mach number of 1.3 and 1.4, respectively. Surface oil-flow visualization is used to study the mean characteristics of the interaction where surface features such as...
Show moreAn experimental study is conducted on the interaction of a swept-shock wave with a turbulent boundary layer. The shock wave is generated by a sharp un-swept fin in a Mach 2 flow, where the strength of the interaction is varied from weak to moderate by changing the fin angle of attack from 10° to 15°, which corresponds to a normal Mach number of 1.3 and 1.4, respectively. Surface oil-flow visualization is used to study the mean characteristics of the interaction where surface features such as the upstream influence and separation line are identified. By taking advantage of the quasi-conical symmetry of the flowfield, two- and three-component velocity field measurements are acquired in the conical reference frame for the interaction of moderate interaction strength (Mn ~ 1.4) at two locations from the fin apex. Flowfield features such as the λ-shock structure, slip line, and the separation bubble with the reverse flow are clearly visible in the in-plane velocity fields. These results are also examined in the spherical coordinate frame, and good agreement in the spatial location of the critical features is found, providing direct quantitative, experimental evidence of quasi-conical symmetry of this flowfield above the surface. An examination of the velocity field downstream of the rear-foot of the λ-shock shows a region - a 'streamtube,' bounded on one side by the slip line emanating from the triple point - where the flow accelerates to transonic and supersonic speeds. This flow eventually turns towards and impinges upon the flat plate, a phenomenon referred to as an 'impinging jet' in literature and is believed to be the principal cause of the high mean, and unsteady pressures, very high heating and skin friction coefficients near impingement. The out-of-plane velocity fields unveiled the presence of a significant radially outward velocity component distinctly showing the presence of an 'open' separation bubble with a flattened conical vortex, a typical characteristic of a 3-D SBLI flowfield. The interaction dynamics are explored through unsteady surface pressure measurements at strategic locations. The highest unsteadiness is observed near the intermittent separation and underneath the open separation bubble. Further insights into the interaction dynamics is sought by examining the contributions to unsteady pressures in three spectral regimes - low-frequency (Stδ < 0.01), mid-frequency (0.01 < Stδ < 0.2) and high-frequency (Stδ > 0.2) to separate the contributions of each band to the total pressure fluctuations. Mid-frequency fluctuations dominate the current 3-D interaction flowfield, in contrast to 2-D SBLI where low-frequency disturbances are shown to be prominent. The spectral behavior shows no discrete peaks. However, relatively high coherence is observed between the intermittent separation region and underneath the separation bubble at Stδ ~ 0.013. It is plausible that the separation and rear shock are undergoing a low-frequency correlated motion, but the energy in this low-frequency periodic motion is found to be much lower than the mid-frequency unsteadiness that dominates this flowfield. Finally, the interaction is visualized using high-frame-rate conical shadowgraphy (24000 fps), where a shock detection scheme is utilized to identify the primary shock features from the instantaneous conical shadowgraphy images. The PDFs of their mean-subtracted spatial locations revealed that the separation shock undergoes the highest range of motion compared to other two shock features. It is inferred that the smaller extent of the λ-shock is more probable, which is further confirmed by the conditional sampling of the separation and rear shock slope based on the upstream or downstream movement of the separation shock. The response of this interaction to unsteady REM perturbations is also studied using three-component velocity and z-vorticity fields. Various REM configurations are tested (A1, A2, and A123) and it is distinctly seen that the A123 actuation most affected the flowfield. From the out-of-plane velocity fields, a significant impact of the REM induced CVPs on the flowfield inside the separation bubble is observed, whereas the inviscid region appears to remain unaltered. A general trend of increase in near-wall vorticity when compared to the baseline case, upstream of the intermittent separation is seen from the z-vorticity fields. Finally, the path of these induced CVPs in this highly 3-D flowfield became evident when these vorticity fields are visualized in conjunction with the surface flow maps from our earlier work.
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Date Issued: 2018
Identifier: 2018_Fall_Arora_fsu_0071E_14877
Format: Thesis

Title: Application of Particle Tracking Velocimetry to Thermal Counterflow and Towed-Grid Turbulence in Helium II.
Creator: Mastracci, Brian, Guo, Wei, Piekarewicz, Jorge, Oates, William, Taira, Kunihiko, Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: The superfluid phase of helium-4, known as He~II, is predominantly used to cool low-temperature devices. It transfers heat by a unique thermally driven counterflow of its two constituents, a classical normal fluid and an inviscid superfluid devoid of entropy. It also has potential use for economical reproduction and study of high Reynolds number turbulent flow due to the extremely small kinematic viscosity and classical characteristics exhibited by mechanically driven flow. A number of...
Show moreThe superfluid phase of helium-4, known as He~II, is predominantly used to cool low-temperature devices. It transfers heat by a unique thermally driven counterflow of its two constituents, a classical normal fluid and an inviscid superfluid devoid of entropy. It also has potential use for economical reproduction and study of high Reynolds number turbulent flow due to the extremely small kinematic viscosity and classical characteristics exhibited by mechanically driven flow. A number of diagnostic techniques have been applied in attempts to better understand the complex behavior of this fluid, but one of the most useful, flow visualization, remains challenging because of complex interactions between foreign tracer particles and the normal fluid, superfluid, and a tangle of quantized vortices that represents turbulence in the superfluid. An apparatus has been developed that enables application of flow visualization using particle tracking velocimetry (PTV) in conjunction with second sound attenuation, a mature technique for measuring quantized vortex line density, to both thermal counterflow and mechanically-driven towed-grid turbulence in He~II. A thermal counterflow data set covering a wide heat flux range and a number of different fluid temperatures has been analyzed using a new separation scheme for differentiating particles presumably entrained by the normal fluid ("G2") from those trapped on quantized vortices ("G1"). The results show that for lower heat flux, G2 particles move at the normal fluid velocity vn, but for higher heat flux all particles move at roughly vn/2 ("G3"). Probability density functions (PDFs) for G1 particle velocity vp are Gaussian curves with tails proportional to |vp|⁻³, which arise from observation of particles trapped on reconnecting vortices. A probable link between G1 velocity fluctuations and fluctuations of the local vortex line velocity has been established and used to provide the first experimental estimation of c₂, a parameter related to energy dissipation in He~II. Good agreement between the length of observed G2 tracks and a simple model for the mean free path of a particle traveling through the vortex tangle suggests that flow visualization may be an alternative to second sound attenuation for measurement of vortex line density in steady-state counterflow. Preliminary PTV and second sound data in decaying He~II towed-grid turbulence shows agreement with theoretical predictions, and enables reliable estimation of an effective kinematic viscosity and calculation of longitudinal and transverse structure functions, from which information about the energy spectrum evolution and intermittency enhancement can be obtained.
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Date Issued: 2018
Identifier: 2018_Fall_Mastracci_fsu_0071E_14818
Format: Thesis

Title: Global Stability Analysis and Control of Compressible Flows over Rectangular Cavities.
Creator: Sun, Yiyang, Taira, Kunihiko, Yu, Weikuan, Cattafesta, Louis N., Ukeiley, Lawrence S., Lin, Shangchao, Florida State University, College of Engineering, Department of Mechanical...
Show moreSun, Yiyang, Taira, Kunihiko, Yu, Weikuan, Cattafesta, Louis N., Ukeiley, Lawrence S., Lin, Shangchao, Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: The present numerical investigation aims to uncover the inherent instability in compressible cavity flows and aid designs of effective flow control to alter undesirable flow features. Two-dimensional (2D) and three-dimensional (3D) global stabilities of compressible open-cavity flows are examined in detail, which provides insights into designs of active flow control to reduce the pressure fluctuations over the cavity. The stability characteristics of compressible spanwise-periodic open-cavity...
Show moreThe present numerical investigation aims to uncover the inherent instability in compressible cavity flows and aid designs of effective flow control to alter undesirable flow features. Two-dimensional (2D) and three-dimensional (3D) global stabilities of compressible open-cavity flows are examined in detail, which provides insights into designs of active flow control to reduce the pressure fluctuations over the cavity. The stability characteristics of compressible spanwise-periodic open-cavity flows are investigated with direct numerical simulation (DNS) and biglobal stability analysis for rectangular cavities with length-to-depth ratios of $L/D=2$ and 6. This study examines the behavior of instabilities with respect to stable and unstable steady states in the laminar regimes for subsonic as well as transonic conditions where compressibility plays an important role. It is observed that an increase in Mach number destabilizes the flow in the subsonic regime and stabilizes the flow in the transonic regime. Biglobal stability analysis for spanwise-periodic flows over rectangular cavities with large aspect ratio is closely examined in this study due to its importance in aerodynamic applications. Moreover, biglobal stability analysis is conducted to extract 2D and 3D eigenmodes for prescribed spanwise wavelengths $\lambda/D$ about the 2D steady state. The properties of 2D eigenmodes agree well with those observed in the 2D DNS. In the analysis of 3D eigenmodes, it is found that an increase of Mach number stabilizes dominant 3D eigenmodes. For a short cavity with $L/D=2$, the 3D eigenmodes primarily stem from centrifugal instabilities. For a long cavity with $L/D=6$, other types of eigenmodes appear whose structures extend from the aft-region to the mid-region of the cavity, in addition to the centrifugal stability mode located in the rear part of the cavity. A selected number of 3D DNS are performed at $M_\infty=0.6$ for cavities with $L/D=2$ and 6. For $L/D=2$, the properties of 3D structures present in the 3D nonlinear flow correspond closely to those obtained from linear stability analysis. However, for $L/D=6$, the 3D eigenmodes cannot be clearly observed in the 3D DNS, due to the strong nonlinearity that develops over the length of the cavity. In addition, it is noted that three-dimensionality in the flow helps alleviate violent oscillations for the long cavity. The analysis performed in this paper can provide valuable insights for designing effective flow control strategies to suppress undesirable aerodynamic and pressure fluctuations in compressible open-cavity flows. Three-dimensional nonlinear simulations (DNS and LES) are also conducted to examine influence of cavity width, sidewall boundary conditions, free stream Mach numbers, and Reynolds numbers on open-cavity flows. DNS and large eddy simulations (LES) are performed with $L/D=6$, width-to-depth ratios of $W/D$=1 and 2 for Reynolds number of $Re_D = 502$ and $10^4$. To numerically study the effects of cavity width on the flows, we consider (1) 2D cavities with spanwise periodicity and (2) finite-span cavities with no-slip adiabatic walls. Furthermore, the analyses are conducted for subsonic ($M_\infty=0.6$) and supersonic ($M_\infty=1.4$) speeds to reveal compressibility effects. It is found that, at low $Re_D=502$, widening the cavity can decrease the velocity fluctuations of the flow by introducing spanwise variations in the shear layer to reduce the kinetic energy from spanwise vortices associated with Rossiter modes. Both velocity and pressure fluctuations decrease in the finite-span cavity compared to those with spanwise periodic boundary conditions. With the characteristics of base flows revealed, flow control is implemented for turbulent cavity flows where steady blowing is introduced along the leading edge of the cavity for both subsonic ($M_\infty=0.6$) and supersonic ($M_\infty=1.4$) flows. We examine how the actuations interact with the flows and reduce the velocity and pressure fluctuations with and without sidewalls. From the control study, we find that pressure reduction on the cavity surfaces can be achieved in an effective manner by taking advantage of 3D flow physics.
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Date Issued: 2017
Identifier: FSU_FALL2017_Sun_fsu_0071E_14244
Format: Thesis

Title: Uncertainty Analysis of Multifunctional Constitutive Relations and Adaptive Structures.
Creator: Miles, Paul R., Oates, William, Hussaini, M. Yousuff, Zeng, Changchun (Chad), Taira, Kunihiko, Lin, Shangchao, Smith, Ralph C., Florida State University, College of Engineering,...
Show moreMiles, Paul R., Oates, William, Hussaini, M. Yousuff, Zeng, Changchun (Chad), Taira, Kunihiko, Lin, Shangchao, Smith, Ralph C., Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: Practically all engineering applications require knowledge of uncertainty. Accurately quantifying uncertainty within engineering problems supports model development, potentially leading to identification of key risk factors or cost reductions. Often the full problem requires modeling behavior of materials or structures from the quantum scale all the way up to the macroscopic scale. Predicting such behavior can be extremely complex, and uncertainty in modeling is often increased due to...
Show morePractically all engineering applications require knowledge of uncertainty. Accurately quantifying uncertainty within engineering problems supports model development, potentially leading to identification of key risk factors or cost reductions. Often the full problem requires modeling behavior of materials or structures from the quantum scale all the way up to the macroscopic scale. Predicting such behavior can be extremely complex, and uncertainty in modeling is often increased due to necessary assumptions. We plan to demonstrate the benefits of performing uncertainty analysis on engineering problems, specifically in the development of constitutive relations and structural analysis of smart materials and adaptive structures. This will be highlighted by a discussion of ferroelectric materials and their domain structure interaction, as well as dielectric elastomers’ viscoelastic and electrostrictive properties.
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Date Issued: 2017
Identifier: FSU_SUMMER2017_Miles_fsu_0071E_14033
Format: Thesis

Title: Experimental Characterization of Photoresponsive Azobenzene Polymers.
Creator: Chowdhury, Sadiyah Sabah, Oates, William, Lin, Shangchao, Ordóñez, Juan Carlos, Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: Azobenzene is a photo responsive polymer which undergoes molecular change under exposure to certain wavelengths of light. This molecular shape change can cause an overall macroscopic shape change in an azobenzene polymer network. This promising photostrictive behavior has broad range of applications in flow control, robotics and energy harvesting applications. The conversion of solar energy directly into mechanical work provides unique capabilities in adaptive structures. In this thesis,...
Show moreAzobenzene is a photo responsive polymer which undergoes molecular change under exposure to certain wavelengths of light. This molecular shape change can cause an overall macroscopic shape change in an azobenzene polymer network. This promising photostrictive behavior has broad range of applications in flow control, robotics and energy harvesting applications. The conversion of solar energy directly into mechanical work provides unique capabilities in adaptive structures. In this thesis, stress measurements show that irradiated azo-LCN experience photochemical and thermomechanical stress. Experimental results show that stress response depends highly on the range of pre-stress applied and the threshold pre-stress differs for different polarization directions.
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Date Issued: 2017
Identifier: FSU_SUMMER2017_Chowdhury_fsu_0071N_13891
Format: Thesis

Title: Investigation of Numerical Modeling Techniques for Gas-Cooled Superconducting Power Devices.
Creator: Suttell, Nicholas George, Ordóñez, Juan Carlos, Pamidi, Sastry V., Li, Hui, Guo, Wei (Professor of Mechanical Engineering), Hollis, Patrick J., Florida State University, FAMU...
Show moreSuttell, Nicholas George, Ordóñez, Juan Carlos, Pamidi, Sastry V., Li, Hui, Guo, Wei (Professor of Mechanical Engineering), Hollis, Patrick J., Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering
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Abstract/Description: Global energy demands are on the rise, and the current technology used to generate, transmit, and distribute electricity will not be able to meet the growth due to the bottlenecks in densely populated areas and the inefficiencies throughout the electrical grid. Soon, new technologies will be required to relieve the constraints on the grid while being cost effective, reliable, and environmentally acceptable. High temperature superconducting (HTS) technology being developed has the means to...
Show moreGlobal energy demands are on the rise, and the current technology used to generate, transmit, and distribute electricity will not be able to meet the growth due to the bottlenecks in densely populated areas and the inefficiencies throughout the electrical grid. Soon, new technologies will be required to relieve the constraints on the grid while being cost effective, reliable, and environmentally acceptable. High temperature superconducting (HTS) technology being developed has the means to provide ways to overcome the challenges faced by electric utility companies. Other applications including all-electric ships and aircrafts would also benefit greatly from the use of HTS power devices in meeting the increasing electrical power requirements at high power densities. HTS power technology is relatively complex, and it involves multiple technological and scientific disciplines besides the materials being expensive currently to enable cost-effective applications. Therefore, intensive numerical modeling efforts are necessary to improve the designs and system level optimizations so that the technology will be commercially viable. The goal of the research described here is to investigate and develop effective methods of modeling and simulating HTS power devices cooled with gaseous helium (GHe) circulation. The technique of GHe-cooled HTS power systems is relatively new, and there is much room for improvements in designs, particularly integrating the superconducting and cryogenics systems. Benefits of modeling the systems in detail include reduced cost and time and the ability to perform optimizations; each of which would allow faster development cycles at lower cost. These benefits arise from the fact that it’s more efficient to design complex systems using bits as opposed to atoms. A 30-m long HTS power cable including the cable terminations and the cryogenic helium circulation system is the primary system studied in this work. GHe offers some important benefits over liquid nitrogen including improved safety in confined spaces and lower operating temperatures especially for superconducting applications that require high power densities such as those to be used on all-electric Navy ships. However, there are still some challenges that need to be addressed. GHe possesses lower heat capacity per unit volume compared to liquid cryogens, and its weak dielectric strength currently restricts its use in HTS power cables at low and medium voltage applications. This dissertation describes numerical modeling techniques including volume element methods and finite element methods that were developed to visualize the physics of several different HTS cable system components. The modelling techniques developed were further utilized for transient analysis of the cryogenic thermal and electrical behavior under various scenarios and system operational contingencies to assess the limitations of the technology and to devise methods for mitigating the contingencies.
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Date Issued: 2017
Identifier: FSU_SUMMER2017_Suttell_fsu_0071E_14075
Format: Thesis

Title: Leg Specialization Control: Deriving Control from the Perspective of Limb Function.
Creator: Carbiener, Charles P., Clark, Jonathan E., Ordonez, Camilo, Xu, Chengying, Collins, Emmanuel G., Florida State University, College of Engineering, Department of Mechanical...
Show moreCarbiener, Charles P., Clark, Jonathan E., Ordonez, Camilo, Xu, Chengying, Collins, Emmanuel G., Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: Many leg controllers and gaits have been designed directly with lower level parameters. This approach can lead to very high performance gaits, but can also lead to platforms highly tuned for one particular application with drastically reduced performance elsewhere. Through the Leg Specialization (LSC) gait strategy presented here, an alternative approach is demonstrated. Designing controllers from the perspective of limb function allows for adaptation to various environments, and here has...
Show moreMany leg controllers and gaits have been designed directly with lower level parameters. This approach can lead to very high performance gaits, but can also lead to platforms highly tuned for one particular application with drastically reduced performance elsewhere. Through the Leg Specialization (LSC) gait strategy presented here, an alternative approach is demonstrated. Designing controllers from the perspective of limb function allows for adaptation to various environments, and here has produced a high performing gait capable of running on a variety of surfaces.
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Date Issued: 2017
Identifier: FSU_SUMMER2017_Carbiener_fsu_0071N_13986
Format: Thesis

Title: Experimental Study of Controlled Surface Imperfection Effects on Vortex Asymmetry of Conical Bodies at High Angles of Incidence.
Creator: Rodriguez, Joseph, Kumar, Rajan (Professor of Mechanical Engineering), Oates, William, Shoele, Kourosh, Florida State University, College of Engineering, Department of...
Show moreRodriguez, Joseph, Kumar, Rajan (Professor of Mechanical Engineering), Oates, William, Shoele, Kourosh, Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: At high angles of attack, asymmetric vortices are formed on the leeward side of flight vehicles with pointed forebodies due to the random surface imperfections near the forebody apex. These vortices induce adverse side forces and yaw moments. The forces generated are too large to be controlled using conventional control surfaces and can result in flight instability and loss of control. Although many studies have reported that random surface imperfections trigger vortex asymmetry, there is a...
Show moreAt high angles of attack, asymmetric vortices are formed on the leeward side of flight vehicles with pointed forebodies due to the random surface imperfections near the forebody apex. These vortices induce adverse side forces and yaw moments. The forces generated are too large to be controlled using conventional control surfaces and can result in flight instability and loss of control. Although many studies have reported that random surface imperfections trigger vortex asymmetry, there is a lack of understanding of how these imperfections directly correlate to the varying side force with roll orientation. The present study is aimed at gaining a better insight into the underlying flow physics of vortex asymmetry. This is accomplished by performing flow field measurements using Particle Image Velocimetry and force measurements using a six-component strain gage balance on an unpolished and a highly-polished 12° semi-apex angle cone at subsonic speeds. Measurements were carried out with and without the implementation of controlled surface imperfections. All experiments were performed at a fixed Reynolds number of 0.3 × 10^6 based on the base diameter of the cone model. The force measurements indicate that the vortices caused by the random surface imperfections are highly dependent on the magnitude of surface roughness. The results show that the side force was significantly reduced and was relatively less dependent on roll orientation for the polished cone. Flow field results show that the ratio of imperfection height to the local cross-flow boundary layer thickness was observed to be critical in influencing the vortex location and growth. Furthermore, the region of incipient boundary layer separation was highly sensitive to the controlled imperfections.
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Date Issued: 2017
Identifier: FSU_SUMMER2017_Rodriguez_fsu_0071N_14107
Format: Thesis

Title: Motion Planning Testing Environment for Robotic Skid-Steered Vehicles.
Creator: Pace, James, Collins, Emmanuel G., Clark, Jonathan E., Ordonez, Camilo, Shoele, Kourosh, Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: One of the main goals of robotics research is to give physical platforms intelligence, allowing for the platforms to act autonomously with minimal direction from humans. Motion planning is the process by which a mobile robot plans a trajectory that moves the robot from one state to another. While there are many motion planning algorithms, this research focuses on Sampling Based Model Predictive Optimization (SBMPO), a motion planning algorithm that allows for the generation of trajectories...
Show moreOne of the main goals of robotics research is to give physical platforms intelligence, allowing for the platforms to act autonomously with minimal direction from humans. Motion planning is the process by which a mobile robot plans a trajectory that moves the robot from one state to another. While there are many motion planning algorithms, this research focuses on Sampling Based Model Predictive Optimization (SBMPO), a motion planning algorithm that allows for the generation of trajectories that are not only dynamically feasible, but also efficient in terms of a user defined cost function (specifically in this research, distance traveled or energy consumed). To accomplish this, SBMPO uses the kinematic, dynamic, and power models of the robot. The kinematic, dynamic, and power models of a skid-steered robot are dependent on the type and inclination of the terrain over which the robot is traversing. Previous research has successfully used SBMPO to plan trajectories on different inclinations and terrain types, but with the terrain type and inclination being held constant over the trajectory. This research extends the prior work to plan trajectories where the terrain type changes over the trajectory and where the robot has the option to go over or around hills, situations extremely common in real world environments encountered in military and search and rescue operations. Furthermore, this research documents the design and implementation of a 3D visualization environment which allows for the visualization of the trajectory generated by the planner without having a robot follow the trajectory in a physical environment.
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Date Issued: 2017
Identifier: FSU_SUMMER2017_Pace_fsu_0071N_14099
Format: Thesis

Title: Active Control of Wingtip Vortices Using Piezoelectric Actuated Winglets.
Creator: Guha, Tufan Kumar, Kumar, Rajan (Professor of Mechanical Engineering), Liang, Zhiyong Richard, Oates, William, Alvi, Farrukh S., Florida State University, FAMU-FSU College of...
Show moreGuha, Tufan Kumar, Kumar, Rajan (Professor of Mechanical Engineering), Liang, Zhiyong Richard, Oates, William, Alvi, Farrukh S., Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering
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Abstract/Description: Wingtip vortices develop at the tips of aircraft wings due to a pressure imbalance during the process of generating lift. These vortices significantly increase the total aerodynamic drag of an aircraft at high-lift flight conditions such as during take-off and landing. The long trailing vortices contain strong circulation and may induce rolling moments and lift losses on a trailing aircraft, making them a major cause for wake turbulence. A mandatory spacing between aircraft is administered by...
Show moreWingtip vortices develop at the tips of aircraft wings due to a pressure imbalance during the process of generating lift. These vortices significantly increase the total aerodynamic drag of an aircraft at high-lift flight conditions such as during take-off and landing. The long trailing vortices contain strong circulation and may induce rolling moments and lift losses on a trailing aircraft, making them a major cause for wake turbulence. A mandatory spacing between aircraft is administered by civil aviation agencies to reduce the probability of hazardous wake encounters. These measures, while necessary, restrict the capacity of major airports and lead to higher wait times between take-off and landing of two aircraft. This poses a major challenge in the face of continuously increasing air traffic volume. Wingtip vortices are also known as a potent source of aerodynamic vibrations and noise. These negative effects have made the study of wingtip vortex attenuation a critical area of research. The problem of induced drag has been addressed with the development of wingtip device, like winglets. Tip devices diffuse the vortex at its very onset leading to lower induced drag. The problem of wake turbulence has been addressed in studies on vortex interactions and co-operative instabilities. These instabilities accelerate the process of vortex breakdown, leading to a lower lifetime in the wake. A few studies have tried to develop active mechanisms that can artificially excite these instabilities. The aim of the present study is to develop a device that can be used for both reducing induced drag and exciting wake instabilities. To accomplish this objective, an active winglet actuator has been developed with the help of piezoelectric Macro-Fiber Composite (MFC). The winglet is capable of oscillating about the main wing-section at desired frequency and amplitude. A passive winglet is a well-established drag reducing device. An oscillating winglet can introduce perturbations that can potentially lead to instabilities and accelerate the process of vortex breakdown. A half-body model of a generic aircraft configuration was fabricated to characterize and evaluate the performance of actuated winglets. Two winglet models having mean dihedral orientations of 0° and 75° were studied. The freestream velocity for these experiments was 20 m/s. The angle of incidence of the wing-section was varied between 0° and 8°. The Reynolds number based on the mid-chord length of the wing-section is 140000. The first part of the study consisted of a detailed structural characterization of the winglets at various input excitation and pressure loading conditions. The second part consisted of low speed wind tunnel tests to investigate the effects of actuation on the development of wingtip vortices at different angles of incidence. Measurements included static surface pressure distributions and Stereoscopic (ensemble and phase-locked) Particle Image Velocimetry (SPIV) at various downstream planes. Modal analysis of the fluctuations existing in the baseline vortex and those introduced by actuation is conducted with the help of Proper Orthogonal Decomposition (POD) technique. The winglet oscillations show bi-modal behavior for both structural and actuation modes of resonance. The oscillatory amplitude at these actuation modes increases linearly with the magnitude of excitation. During wind tunnel tests, fluid structure interactions lead to structural vibrations of the wing. The effect of these vibrations on the winglet oscillations decreases with the increase in the strength of actuation. At high input excitation, the actuated winglet is capable of generating controlled oscillations suitable for perturbing the vortex. The vortex associated with a winglet is stretched along its axis with multiple vorticity peaks. The center of the vortex core is seen at the root of the winglet while the highest vorticity levels are observed at the tip. The vortex core rotates and becomes more circular in shape while diffusing downstream. The shape, position, and strength of the vorticity peaks are found to vary periodically with winglet oscillation. Actuation is even capable of disintegrating the single vortex core into two vortices. The most energetic POD fluctuation modes, at the center of the baseline vortex core, correspond to vortex wandering at the initial downstream planes. At the farthest planes, the most energetic modes can be associated with core deformation. High energy fluctuations in the actuated vortex correspond to spatial oscillations and distortions produced by the winglet motion.
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Date Issued: 2017
Identifier: FSU_SUMMER2017_Guha_fsu_0071E_14000
Format: Thesis

Title: Aeroacoustic Characteristics of Supersonic Impinging Jets.
Creator: Worden, Theodore James, Alvi, Farrukh S., Shih, Chiang, Liang, Zhiyong Richard, Collins, Emmanuel G., Gustavsson, Jonas, Kumar, Rajan (Professor of Mechanical Engineering),...
Show moreWorden, Theodore James, Alvi, Farrukh S., Shih, Chiang, Liang, Zhiyong Richard, Collins, Emmanuel G., Gustavsson, Jonas, Kumar, Rajan (Professor of Mechanical Engineering), Michalis, Krista, Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: High-speed impinging jets are often generated by the propulsive systems of aerospace launch vehicles and tactical aircraft. In many instances, the presence of these impinging jets creates a hazard for flight operations personnel due to the extremely high noise levels and unsteady loads produced by fluid-surface interaction. In order to effectively combat these issues, a fundamental understanding of the flow physics and dominant acoustic behavior is essential. There are inherent challenges in...
Show moreHigh-speed impinging jets are often generated by the propulsive systems of aerospace launch vehicles and tactical aircraft. In many instances, the presence of these impinging jets creates a hazard for flight operations personnel due to the extremely high noise levels and unsteady loads produced by fluid-surface interaction. In order to effectively combat these issues, a fundamental understanding of the flow physics and dominant acoustic behavior is essential. There are inherent challenges in performing such investigations, especially with the need to simulate the flowfield under realistic operational conditions (temperature, Mach number, etc.) and in configurations that are relevant to full-scale application. A state-of-the-art high-temperature flow facility at Florida State University has provided a unique opportunity to experimentally investigate the high-speed impinging jet flowfield at application-relevant conditions. Accordingly, this manuscript reports the findings of several experimental studies on high-temperature supersonic impinging jets in multiple configurations. The overall objective of these studies is to characterize the complex relationship between the hydrodynamic and acoustic fields. A fundamental parametric investigation has been performed to document the flowfield and acoustic characteristics of an ideally-expanded supersonic air jet impinging onto a semi-infinite flat plate at ambient and heated jet conditions. The experimental program has been designed to span a widely-applicable geometric parameter space, and as such, an extensive database of the flow and acoustic fields has been developed for impingement distances in the range 1d to 12d, impingement angles in the range 45 degrees to 90 degrees, and jet stagnation temperatures from 289K to 811K (TTR=1.0 to 2.8). Measurements include point-wise mean and unsteady pressure on the impingement surface, time-resolved shadowgraphy of the flowfield, and fully three-dimensional near field acoustics. Aside from detailed documentation of the flow and acoustic fields, this work aims to develop a physical understanding of the noise sources generated by impingement. Correlation techniques are employed to localize and quantify the spatial extent of broadband noise sources in the near-impingement region and to characterize their frequency content. Additionally, discrete impingement tones are documented for normal and oblique incidence angles, and an empirical model of the tone frequencies has been developed using velocity data extracted from time-resolved shadowgraphy together with a simple modification to the conventional feedback formula to account for non-normal incidence. Two application-based studies have also been undertaken. In simulating a vertical take-off and landing aircraft in hover, the first study of a normally-impinging jet outfitted with lift-plate characterizes the flow-acoustic interaction between the high-temperature jet and the underside of an aircraft and documents the effectiveness of an active flow control technique known as `steady microjet injection' to mitigate high noise levels and unsteady phenomena. The second study is a detailed investigation of the jet blast deflector/carrier deck configuration aimed at gaining a better understanding of the noise field generated by a jet operating on a flight deck. The acoustic directionality and spectral characteristics are documented for a model-scale carrier deck with particular focus on locations that are pertinent to flight operations personnel.
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Date Issued: 2017
Identifier: FSU_SUMMER2017_Worden_fsu_0071E_13997
Format: Thesis

Title: Characterization of the Flow-Field for Dual Normally Impinging Axi-Symmetric Jets.
Creator: Harmon, Malcolm Jerrod, Alvi, Farrukh S., Kumar, Rajan (Professor of Mechanical Engineering), Collins, Emmanuel G., Florida State University, College of Engineering, Department...
Show moreHarmon, Malcolm Jerrod, Alvi, Farrukh S., Kumar, Rajan (Professor of Mechanical Engineering), Collins, Emmanuel G., Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: In this study, the flow and acoustic field characteristics of dual high-speed axi-symmetric impinging jets will be examined. Initially, the short takeoff and vertical landing (STOVL) facility was redesigned by adding a second jet to the existing model there by achieving a dual jet configuration. This modified facility was designed to simulate aircraft hover in proximity to the ground. Emphasis is placed on the complex behavior of the jets as the nozzle pressure ratio (NPR) is varied to...
Show moreIn this study, the flow and acoustic field characteristics of dual high-speed axi-symmetric impinging jets will be examined. Initially, the short takeoff and vertical landing (STOVL) facility was redesigned by adding a second jet to the existing model there by achieving a dual jet configuration. This modified facility was designed to simulate aircraft hover in proximity to the ground. Emphasis is placed on the complex behavior of the jets as the nozzle pressure ratio (NPR) is varied to produce over-expanded, ideally-expanded and under-expanded jet flows. Two nozzle configurations were chosen to simulate dual impinging jets: 1) two converging nozzles (Mach design, Md = 1.00) and 2) a converging nozzle (Md = 1.00) and a converging-diverging (CD) nozzle (Md = 1.50). The experimental results described in this thesis include shadowgraph flow visualization, surface pressure measurements, and near-field acoustic measurements. Shadowgraph flow visualization was used to observe the acoustic field and the coupling between dual jets for various NPR combinations. Mean surface pressure measurements were obtained for impinging jet configurations which analyzed the jet behavior for ground plane separations ranging from x/D = 2 to 10. These measurements provided information regarding the footprint of the flow-field, particularly the fountain flow behavior. It was found that there is a shift in the fountain flow region which occurs when the NPR of one jet was substantially higher than the supplementary jet. Unsteady pressure measurements and near-field acoustic measurements investigated the presence of a feedback loop that occurs for both free and impinging jets, under certain conditions. The presence of tones, either screech or impingement, was clearly evident from the spectral peaks in the near-field noise spectra. When such tones are present, the corresponding flow-field images show strong acoustic waves.
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Date Issued: 2017
Identifier: FSU_SUMMER2017_Harmon_fsu_0071N_14049
Format: Thesis

Title: A Novel Mixed Reality Interface for Effective and Efficient Human Robot Interaction with Unique Mobility Platforms.
Creator: Kopinsky, Ryan J., Collins, Emmanuel G., Roberts, Rodney G., Clark, Jonathan E., Oates, William, Barber, Daniel J., Florida State University, College of Engineering, Department...
Show moreKopinsky, Ryan J., Collins, Emmanuel G., Roberts, Rodney G., Clark, Jonathan E., Oates, William, Barber, Daniel J., Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: Autonomous robots are increasingly working alongside humans in a variety of environments. While simple applications in controlled environments work fine with fully autonomous robots and little interaction between human and robot, mission-critical applications in unstructured and uncertain environments require a stronger collaboration between human and robot. An example of such an instance occurs in dismounted military operations in which one or more autonomous robots act as part of a team of...
Show moreAutonomous robots are increasingly working alongside humans in a variety of environments. While simple applications in controlled environments work fine with fully autonomous robots and little interaction between human and robot, mission-critical applications in unstructured and uncertain environments require a stronger collaboration between human and robot. An example of such an instance occurs in dismounted military operations in which one or more autonomous robots act as part of a team of soldiers. The performance of the human-robot team depends largely on the interaction between human and robot, more specifically the communication interfaces between the two. Furthermore, due to the complex and unstructured environments in which dismounted military missions take place, robots need to have a diverse skill set. Therefore, a variety of sensors, robot platform types (e.g. wheeled vs legged) and other capabilities are needed. The goal of this research was to understand how robot platform type and visual complexity of the human-robot interface, in particular a Mixed Reality interface, affect cooperative human-robot teaming in dismounted military operations. More specifically, the research objectives were to understand how robot platform type (wheeled vs. legged) impacts the human's perception of robot capability and performance, and to assess how visual complexity of a Mixed Reality interface affects accuracy and response time for an information reporting task and a signal detection task. The results of this study revealed that an increased visual complexity of the Mixed Reality-based human-robot interface improved response time and accuracy for an information reporting task and resulted in a more usable interface. Furthermore, the results indicated that the response time and accuracy for a signal detection task did not differ between high visual complexity and low visual complexity modes of the human-robot interface, which was likely due to a low task load. Users of the interface in high visual complexity mode reported lower perceived workload and better perceived performance compared to users of the interface in low visual complexity mode. Moreover, the findings of this study demonstrated that the unique appearance of a biologically-inspired legged robot was not enough to result in a difference in perceived performance and trust compared to a more traditional- looking wheeled robot. Therefore, there was no basis to conclude that the unique appearance of the legged robot resulted in the user anthropomorphizing the legged robot more than the wheeled robot. Additionally, free response feedback from users revealed that Mixed Reality-based head-mounted displays have the potential to overcome the shortcomings of Augmented Reality-based head-mounted displays and offer a suitable alternative to hand-held displays in dismounted military operations. Finally, this study demonstrated that an increase in visual complexity of a Mixed Reality-based human-robot interface results in improved effectiveness of human robot interaction and ultimately human-robot team performance as long as the additional complexity supports the tasks of the human.
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Date Issued: 2017
Identifier: FSU_SUMMER2017_Kopinsky_fsu_0071E_14062
Format: Thesis

Title: Active Flow Control and Global Stability Analysis of Separated Flow over a NACA 0012 Airfoil.
Creator: Munday, Phillip M. (Phillip Michael), Taira, Kunihiko, Hussaini, M. Yousuff, Alvi, Farrukh S., Cattafesta, Louis N., Lin, Shangchao, Florida State University, College of...
Show moreMunday, Phillip M. (Phillip Michael), Taira, Kunihiko, Hussaini, M. Yousuff, Alvi, Farrukh S., Cattafesta, Louis N., Lin, Shangchao, Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: The objective of this computational study is to examine and quantify the influence of fundamental flow control inputs in suppressing flow separation over a canonical airfoil. Most flow control studies to this date have relied on the development of actuator technology, and described the control input based on specific actuators. Taking advantage of a computational framework, we generalize the inputs to fundamental perturbations without restricting inputs to a particular actuator. Utilizing...
Show moreThe objective of this computational study is to examine and quantify the influence of fundamental flow control inputs in suppressing flow separation over a canonical airfoil. Most flow control studies to this date have relied on the development of actuator technology, and described the control input based on specific actuators. Taking advantage of a computational framework, we generalize the inputs to fundamental perturbations without restricting inputs to a particular actuator. Utilizing this viewpoint, generalized control inputs aim to aid in the quantification and support the design of separation control techniques. This study in particular independently introduces wall-normal momentum and angular momentum to the separated flow using swirling jets through model boundary conditions. The response of the flow field and the surface vorticity fluxes to various combinations of actuation inputs are examined in detail. By closely studying different variables, the influence of the wall-normal and angular momentum injections on separated flow is identified. As an example, open-loop control of fully separated, incompressible flow over a NACA 0012 airfoil at α = 6° and $9° with Re = 23,000 is examined with large-eddy simulations. For the shallow angle of attack α = 6°, the small recirculation region is primarily affected by wall-normal momentum injection. For a larger separation region at α = 9°, it is observed that the addition of angular momentum input to wall-normal momentum injection enhances the suppression of flow separation. Reducing the size of the separated flow region significantly impacts the forces, and in particular reduces drag and increases lift on the airfoil. It was found that the influence of flow control on the small recirculation region (α = 6°) can be sufficiently quantified with the traditional coefficient of momentum. At α = 9°, the effects of wall-normal and angular momentum inputs are captured by modifying the standard definition of the coefficient of momentum, which successfully characterizes suppression of separation and lift enhancement. The effect of angular momentum is incorporated into the modified coefficient of momentum by introducing a characteristic swirling jet velocity based on the non-dimensional swirl number. With the modified coefficient of momentum, this single value is able to categorize controlled flows into separated, transitional, and attached flows. With inadequate control input (separated flow regime), lift decreased compared to the baseline flow. Increasing the modified coefficient of momentum, flow transitions from separated to attached and accordingly results in improved aerodynamic forces. Modifying the spanwise spacing, it is shown that the minimum modified coefficient of momentum input required to begin transitioning the flow is dependent on actuator spacing. The growth (or decay) of perturbations can facilitate or inhibit the influence of flow control inputs. Biglobal stability analysis is considered to further analyze the behavior of control inputs on separated flow over a symmetric airfoil. Assuming a spanwise periodic waveform for the perturbations, the eigenvalues and eigenvectors about a base flow are solved to understand the influence of spanwise variation on the development of the flow. Two algorithms are developed and validated to solve for the eigenvalues of the flow: an algebraic eigenvalue solver (matrix based) and a time-stepping algorithm. The matrix based approach is formulated without ever storing the matrices, creating a computationally memory efficient algorithm. Based on the matrix based solver, eigenvalues and eigenvectors are identified for flow over a NACA 0015 airfoil at Re = 200, $600, and $1,000. All three cases contain similar modes, although the growth rate of the leading eigenvalue is decreased with increasing Reynolds number. Three distinct types of modes are found, wake mode, steady mode, and modes of the continuous branch. While this method is limited in the range of Reynolds numbers, these results are used to validate the time-stepper approach. Increasing the Reynolds number to Re = 23,000 over a NACA 0012 airfoil, the time-stepper method is implemented due to rising computational cost of the matrix-based method. Stability analysis about the time-averaged flow is performed for spanwise wavenumbers of β = 1$, $10π, and $20π, which the latter two wavenumbers are representative of the spanwise spacing between the actuators. The largest spanwise wavelength (β = 1$) contained unstable modes that ranged from low to high frequency, and a particular unstable low-frequency mode corresponding to a frequency observed in the lift forces of the baseline large-eddy simulation. For the larger spanwise wavenumbers, β = 10π ($L_z/c = 0.2$) and $20π ($L_z/c = 0.1$), low-frequency modes were damped and only modes with $f > 5$ were unstable. These results help us gain further insight into the influence of the flow control inputs. Flow control is not implemented in a manner to directly excite specific modes, but does dictate the spanwise wavelengths that can be generated. Comparing the unstable eigenmodes at these two spacings, the larger spanwise spacing ($\beta = 10\pi$) had a greater growth rate for the majority of the unstable modes. The smaller spanwise spacing ($\beta = 20\pi$) has only a single unstable mode with a growth rate an order of magnitude smaller than $\beta = 10\pi$. With the aid of the increased growth rate, perturbations to the flow with a wider spacing become more effective by interacting with natural modes of the flow. Taking advantage of these natural modes allows for decreased input for the wider spanwise spacing. In conclusion, it was shown that the influence of wall-normal and angular momentum inputs on fully separated flow can adequately be described by the modified coefficient of momentum. Through further analysis and the development of a biglobal stability solver, spanwise spacing effects observed in the flow control study can be explained. The findings from this study should aid in the development of more intelligently designed flow control strategies and provide guidance in the selection of flow control actuators.
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Date Issued: 2017
Identifier: FSU_2017SP_Munday_fsu_0071E_13086
Format: Thesis

Title: Characterization of Supersonic Flow Around a Hemispherical Model.
Creator: Carnrike, Daniel Andrew, Kumar, Rajan, Cattafesta, Louis N., Collins, E. (Emmanuel), Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: Propagation of laser beams through complex flow field caused by radar system housing has been an important topic for many years dating back to the mid 1960s. Applications for radar systems range from missile defense, directed energy to target designation and tracking. Complications are introduced when laser systems are no longer stationed on the ground, but instead mounted on airplanes traveling at subsonic, transonic and supersonic speeds. Housing systems have been developed with a variety...
Show morePropagation of laser beams through complex flow field caused by radar system housing has been an important topic for many years dating back to the mid 1960s. Applications for radar systems range from missile defense, directed energy to target designation and tracking. Complications are introduced when laser systems are no longer stationed on the ground, but instead mounted on airplanes traveling at subsonic, transonic and supersonic speeds. Housing systems have been developed with a variety of different designs with some designs more optimal for decreasing laser aberrations than others. The work presented strives to characterize flow around a hemispherical configuration (D = 10.16 cm) for a turret housing system in the supersonic flow regime. Multiple diagnostic tests were conducted at the Florida Center for Advanced Aero-Propulsion in the Polysonic Wind Tunnel Facility. Shadowgraph visualization, surface oil flow visualization, static pressure and unsteady pressure data characterized the complicated supersonic flow field around a hemisphere. Observations were conducted at Mach 2 while Reynolds number changed, ReD = 1.8 ∗ 106 and ReD = 3.6 ∗ 106. Complex shock system consisting of a lambda shock and detached bow shock were observed upstream of the hemisphere center through shadowgraph images. While a shock-let system was developed between the foot of the lambda shock and the detached bow shock from the unsteady boundary layer shockwave interaction. Surface oil flow visualization accented the development of an axisymmetric horseshoe vortex and the presence of a secondary shock location upstream of the hemisphere. A centerline static pressure distribution quantified the visualization techniques. A stagnation point of 30◦ was observed on the body for both ReD case. While, flow separation occurred at slightly different locations on the hemisphere; flow separated at 103◦ for ReD = 1.8∗106 and 107◦ for the ReD = 3.6 ∗ 106. Location of flow separation is further strengthen by the unsteady pressure data as the energy fluctuations are less on the separation line for the different Re cases. The study found that flow structures for different ReD cases were similar, except for the strength of the different flow features; as the flow feature magnitudes were greater for ReD = 3.6 ∗ 106 case. Also observed from the unsteady pressure measurement data, the wake structure behind the hemisphere were different in nature as the wake structure for the ReD = 1.8 ∗ 106 case was larger than the ReD = 3.6 ∗ 106 case. Planar Particle Image Velocimetry was conducted in the Pilot Wind Tunnel Facility at the Florida Center for Advanced Aero-Propulsion on a dynamically similar flow (M = 2,ReD = 1.8∗106). Planar PIV for different Z/D planes were also measured on a D = 19.05 mm hemisphere, which highlighted the presence of an expansion fan at the apex of the hemisphere with decreasing effects on the external flow field as flow moved further away from the centerline of the hemisphere. The results presented in this work characterized supersonic flow around a hemisphere and has laid the groundwork for the development of active or passive flow control techniques in order to minimize flow structures, which ultimately lead to less aero-optical aberrations.
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Date Issued: 2017
Identifier: FSU_FALL2017_Carnrike_fsu_0071N_14262
Format: Thesis

Title: Ultrafast Laser Machining of Dielectrics: A Sharp Interface Model.
Creator: Woerner, Peter Christopher, Oates, William, Lin, Shangchao, Guo, Wei, Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: High temperature pressure sensing is desirable for a broad range of applications related to re-entry of space vehicles and control of combustion processes; however, limited materials can sustain temperatures above 1000C while under time-varying pressure. A sapphire based optical pressure transducer has been proposed for measuring pressure at temperatures approaching 1600C. Manufacturing such sensors has focused on picosecond laser machining. Current research has produced models which can...
Show moreHigh temperature pressure sensing is desirable for a broad range of applications related to re-entry of space vehicles and control of combustion processes; however, limited materials can sustain temperatures above 1000C while under time-varying pressure. A sapphire based optical pressure transducer has been proposed for measuring pressure at temperatures approaching 1600C. Manufacturing such sensors has focused on picosecond laser machining. Current research has produced models which can predict ablation depth for longer (ns) pulses and shorter (fs) pulses but there is an underwhelming amount of research focusing on predicting and understanding the mechanics of picosecond pulses. This is partially because of transitions in the mode of ablation processes associated with photothermal versus photochemical behavior. We put forth a general model for laser ablation using Maxwell's equations and a sharp interface equation and compare different constitutive laws which couple the two equations together. The proposed modeling results are compared to laser machining experimental data on sapphire from the literature to illustrate key material parameter uncertainty and sensitivity to the laser machining process. Bayesian uncertainty quantification is used to help validate the approximations within the constitutive equations.
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Date Issued: 2016
Identifier: FSU_FALL2017_Woerner_fsu_0071N_13473
Format: Thesis

Title: Characterization and Validation of an Anechoic Facility for High-Temperature Jet Noise Studies.
Creator: Craft, Joseph Michael, Alvi, Farrukh S., Kumar, Rajan, Collins, Emmanuel G., Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: In response to the increasing demand for jet noise studies performed at realistic conditions, the Florida Center For Advanced Aero-Propulsion at Florida State University has recently brought online an upgraded Anechoic High-Temperature Jet Facility. The function of this facility is to accurately simulate and characterize the aeroacoustic properties of exhaust from jet engines at realistic temperatures and flow speeds. This new addition is a blow-down facility supplied by a 3500 kPa, 114 cubic...
Show moreIn response to the increasing demand for jet noise studies performed at realistic conditions, the Florida Center For Advanced Aero-Propulsion at Florida State University has recently brought online an upgraded Anechoic High-Temperature Jet Facility. The function of this facility is to accurately simulate and characterize the aeroacoustic properties of exhaust from jet engines at realistic temperatures and flow speeds. This new addition is a blow-down facility supplied by a 3500 kPa, 114 cubic meter compressed dry air system and a sudden-expansion ethylene burner that is capable of producing ideally expanded jets up to Mach 2.6 and stagnation temperatures up to 1500 K. The jet exhausts into a fully anechoic chamber which is equipped to acquire acoustic and flow measurements including the temperature and pressure of the jet. The facility is capable of operating under free jet as well as in various impinging jet configurations pertinent to sea- and land-based aircraft, such as the F-35B. Compared to the original facility, the updated rig is capable of longer run times at higher temperatures. In this paper we demonstrate the facility's experimental capabilities and document jet aeroacoustic characteristics at various flow and temperature conditions. The anechoic chamber was characterized using ISO (3745:2003) guidelines and the lower cutoff frequency of the chamber was determined to be 315 Hz. Aeroacoustic properties of jets operating at subsonic conditions and supersonic Mach numbers ranging from 1.2 to 2.1 at temperatures of ~300 K to ~1300 K are documented. Where available, very good agreement was found when the present results were compared with data in the jet noise literature.
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Date Issued: 2016
Identifier: FSU_FA2016_Craft_fsu_0071N_13535
Format: Thesis

Title: The Development of a Volume Element Model for Energy Systems Engineering and Integrative Thermodynamic Optimization.
Creator: Yang, Sam, Kopriva, David A., Hruda, Simone P. (Simone Peterson), Van Sciver, Steven W., Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: The dissertation presents the mathematical formulation, experimental validation, and application of a volume element model (VEM) devised for modeling, simulation, and optimization of energy systems in their early design stages. The proposed model combines existing modeling techniques and experimental adjustment to formulate a reduced-order model, while retaining sufficient accuracy to serve as a practical system-level design analysis and optimization tool. In the VEM, the physical domain...
Show moreThe dissertation presents the mathematical formulation, experimental validation, and application of a volume element model (VEM) devised for modeling, simulation, and optimization of energy systems in their early design stages. The proposed model combines existing modeling techniques and experimental adjustment to formulate a reduced-order model, while retaining sufficient accuracy to serve as a practical system-level design analysis and optimization tool. In the VEM, the physical domain under consideration is discretized in space using lumped hexahedral elements (i.e., volume elements), and the governing equations for the variable of interest are applied to each element to quantify diverse types of flows that cross it. Subsequently, a system of algebraic and ordinary differential equations is solved with respect to time and scalar (e.g., temperature, relative humidity, etc.) fields are obtained in both spatial and temporal domains. The VEM is capable of capturing and predicting dynamic physical behaviors in the entire system domain (i.e., at system level), including mutual interactions among system constituents, as well as with their respective surroundings and cooling systems, if any. The VEM is also generalizable; that is, the model can be easily adapted to simulate and optimize diverse systems of different scales and complexity and attain numerical convergence with sufficient accuracy. Both the capability and generalizability of the VEM are demonstrated in the dissertation via thermal modeling and simulation of an Off-Grid Zero Emissions Building, an all-electric ship, and a vapor compression refrigeration (VCR) system. Furthermore, the potential of the VEM as an optimization tool is presented through the integrative thermodynamic optimization of a VCR system, whose results are used to evaluate the trade-offs between various objective functions, namely, coefficient of performance, second law efficiency, pull-down time, and refrigerated space temperature, in both transient and steady-state operations.
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Date Issued: 2016
Identifier: FSU_2016SU_Yang_fsu_0071E_13370
Format: Thesis

Title: Development of Operations Manual and Restoration of Cryogenic System for Magnetic Levitation.
Creator: Wray, Andrew, Guo, Wei, Ordóñez, Juan Carlos, Hahn, Seung Yong, Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: The simulation and study of fluid properties and dynamics in a microgravity environment on the Earth’s surface is of great interest due to the high costs associated with conducting research in space. Cryogenic fluids like liquid helium, hydrogen, and oxygen have numerous applications in space travel and research. An understanding of their sloshing motion and general dynamics in microgravity is extremely valuable for maintaining proper orientation of spacecraft and proper cooling. The ability...
Show moreThe simulation and study of fluid properties and dynamics in a microgravity environment on the Earth’s surface is of great interest due to the high costs associated with conducting research in space. Cryogenic fluids like liquid helium, hydrogen, and oxygen have numerous applications in space travel and research. An understanding of their sloshing motion and general dynamics in microgravity is extremely valuable for maintaining proper orientation of spacecraft and proper cooling. The ability to study fluids with no surfaces in contact with their container allows greater flexibility in the study such fluid dynamics, and enables deeper research into quantum turbulence to be conducted. Simulating this microgravity environment on the earth is highly desirable, and may be achieved by using drop towers, acoustic levitation, laser levitation, zero-g planes, and superconducting magnets. The stable magnetic levitation of diamagnetic fluids against the pull of gravity on the earth’s surface may be obtained by generating a strong magnetic field and specific magnetic field gradient. Stability of a levitated liquid drop requires a potential minimum to hold the drop along a central axis, with a field magnitude increasing with increasing radial displacement. The NHMFL cryogenics lab obtained a unique cryostat containing such a magnet, which was used for hydrogen and helium levitation, but which was in disrepair. This cryogenic facility arrived with dozens of leaks and no documentation explaining its structure, functions, or the procedures necessary to use it experimentally. The purpose of this thesis work has been to develop a complete understanding of this cryostat’s structures and functions, as well as the refinement of procedures to properly cool it down and safely operate its magnet. A user manual has been produced to fully document the experimental setup and all necessary procedures. Because this cryostat was received in such bad condition, much time was also committed to the identification of all its mechanical failures, vacuum and gas leaks, and their full repair. Additionally, all supporting pumping systems and gas handling systems were designed, constructed, and documented to facilitate proper and safe operation. Documenting and developing this cryogenic system required extensive designs for external controls and modifications to the system as a whole.
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Date Issued: 2016
Identifier: FSU_2016SU_Wray_fsu_0071N_13463
Format: Thesis

Title: Flow Field and Acoustic Characterization of Non-Axisymmetric Jets.
Creator: Valentich, Griffin Michael, Kumar, Rajan, Alvi, Farrukh S., Lin, Shangchao, Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: Asymmetric jets are becoming more prevalent and may offer significant advantages over traditional axisymmetric nozzles for propulsion as well as fluidic mixing applications. The purpose of this work is two fold: 1) to investigate the effect nozzle exit geometry has on jet development and far field radiated noise of M = 0:9 jets and 2) to study the effect various levels of screech tone self excitation has on jet evolution and the production of streamwise vorticity. Three converging nozzles of...
Show moreAsymmetric jets are becoming more prevalent and may offer significant advantages over traditional axisymmetric nozzles for propulsion as well as fluidic mixing applications. The purpose of this work is two fold: 1) to investigate the effect nozzle exit geometry has on jet development and far field radiated noise of M = 0:9 jets and 2) to study the effect various levels of screech tone self excitation has on jet evolution and the production of streamwise vorticity. Three converging nozzles of various exit geometry (rectangular, elliptic, and round) were utilized to perform the first study, while a supersonic rectangular nozzle was employed to complete the second. All asymmetric nozzles in this work had an aspect ratio of 4:1. To study the flow field features, two dimensional streamwise particle image velocimetry (PIV) as well as three component PIV at select cross planes was performed. Far field acoustic measurements were acquired for the converging nozzles to determine the differences exhibited in the radiated exhaust noise from the major and minor axes of the asymmetric jets compared to the round jet. In comparing the effect exit geometry has on the development of a M = 0:9 jet, it was determined that the shear layers in the major and minor axes developed at similar rates, however, the jet half width in the minor axis exhibited a larger growth rate than the major axis. It was also determined that neither of the asymmetric sonic jets exhibited the axis-switching phenomenon within the measurement domain. Significant streamwise vorticity is noted on the low speed side of the shear layer for the asymmetric jets in the corner regions and areas of small curvature. Moreover, this streamwise vorticity was observed to significantly effect the jet half width in the major axis of the elliptic jet. Acoustic results reveal that there is a strong dependence on frequency range concerning the amount of energy propagated to the far field for each different jet and axis. At low frequencies, the round jet is louder than both axes of the asymmetric jets at polar angles larger than 110°. As the investigated range of frequencies is increased, the primary direction of propagation of noise shifts towards sideline angles for all jets and axes. At the highest range of frequencies investigated, the minor axis of the asymmetric jets produced more noise compared to the equivalent round jet while considerably less noise is produced at polar angles of about 120° – 130° in the major axis direction. Overall sound pressure levels (OASPL) show that the OASPL from the rectangular jet in the plane containing the major axis is lower than the equivalent round jet for aft quadrant angles; the main contributor to the overall reduction is from the highest frequency components. In order to determine the impact screech tone amplitude has on jet development, flow field characteristics of a moderate aspect ratio supersonic rectangular jet were examined at two overexpanded, a perfectly expanded, and an underexpanded jet conditions. The underexpanded and one overexpanded operating condition were of maximum screech, while the second overexpanded condition was of minimum screech intensity. The results show that streamwise vortices present at the nozzle corners along with vortices excited by screech tones play a major role in the jet evolution. The location of streamwise vortex amplification in cases of screech is strongly tied to the downstream shock cell number and the traditional source of the screech tone. All cases except for the perfectly expanded operating condition exhibited axis switching at streamwise locations ranging from 11 to 16 nozzle heights, h, downstream of the exit. The overexpanded condition of maximum screech showed the most upstream switch over, while the underexpanded case showed the farthest downstream. Both of the maximum screeching cases developed into a diamond cross sectional profile far downstream of the exit, while the ideally expanded case maintained a rectangular shape. The overexpanded minimum screeching case eventually decayed into an oblong profile.
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Date Issued: 2016
Identifier: FSU_2016SP_Valentich_fsu_0071N_13176
Format: Thesis

Title: Modeling and Optimization of a Concentrated Solar Supercritical CO2 Power Plant.
Creator: Osorio, Julian David, Ordonez, Juan Carlos, Rivera-Alvarez, Alejandro, Li, Hui, Taira, Kunihiko, Moore, Carl A., Hovsapian, Zohrob O., Florida State University, FAMU-FSU College...
Show moreOsorio, Julian David, Ordonez, Juan Carlos, Rivera-Alvarez, Alejandro, Li, Hui, Taira, Kunihiko, Moore, Carl A., Hovsapian, Zohrob O., Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering
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Abstract/Description: Renewable energy sources are fundamental alternatives to supply the rising energy demand in the world and to reduce or replace fossil fuel technologies. In order to make renewable-based technologies suitable for commercial and industrial applications, two main challenges need to be solved: the design and manufacture of highly efficient devices and reliable systems to operate under intermittent energy supply conditions. In particular, power generation technologies based on solar energy are one...
Show moreRenewable energy sources are fundamental alternatives to supply the rising energy demand in the world and to reduce or replace fossil fuel technologies. In order to make renewable-based technologies suitable for commercial and industrial applications, two main challenges need to be solved: the design and manufacture of highly efficient devices and reliable systems to operate under intermittent energy supply conditions. In particular, power generation technologies based on solar energy are one of the most promising alternatives to supply the world energy demand and reduce the dependence on fossil fuel technologies. In this dissertation, the dynamic behavior of a Concentrated Solar Power (CSP) supercritical CO2 cycle is studied under different seasonal conditions. The system analyzed is composed of a central receiver, hot and cold thermal energy storage units, a heat exchanger, a recuperator, and multi-stage compression-expansion subsystems with intercoolers and reheaters between compressors and turbines respectively. The effects of operating and design parameters on the system performance are analyzed. Some of these parameters are the mass flow rate, intermediate pressures, number of compression-expansion stages, heat exchangers' effectiveness, multi-tank thermal energy storage, overall heat transfer coefficient between the solar receiver and the environment and the effective area of the recuperator. Energy and exergy models for each component of the system are developed to optimize operating parameters in order to lead to maximum efficiency. From the exergy analysis, the components with high contribution to exergy destruction were identified. These components, which represent an important potential of improvement, are the recuperator, the hot thermal energy storage tank and the solar receiver. Two complementary alternatives to improve the efficiency of concentrated solar thermal systems are proposed in this dissertation: the optimization of the system's operating parameters and optimization of less efficient components. The parametric optimization is developed for a 1MW reference CSP system with CO2 as the working fluid. The component optimization, focused on the less efficient components, comprises some design modifications to the traditional component configuration for the recuperator, the hot thermal energy storage tank and the solar receiver. The proposed optimization alternatives include the heat exchanger's effectiveness enhancement by optimizing fins shapes, multi-tank thermal energy storage configurations for the hot thermal energy storage tank and the incorporation of a transparent insulation material into the solar receiver. Some of the optimizations are conducted in a generalized way, using dimensionless models to be applicable no only to the CSP but also to other thermal systems. This project is therefore an effort to improve the efficiency of power generation systems based on solar energy in order to make them competitive with conventional fossil fuel power generation devices. The results show that the parametric optimization leads the system to an efficiency of about 21% and a maximum power output close to 1.5 MW. The process efficiencies obtained in this work, of more than 21%, are relatively good for a solar-thermal conversion system and are also comparable with efficiencies of conversion of high performance PV panels. The thermal energy storage allows the system to operate for several hours after sunset. This operating time is approximately increased from 220 to 480 minutes after optimization. The hot and cold thermal energy storage also lessens the temperature fluctuations by providing smooth changes of temperatures at the turbines' and compressors' inlets. Additional improvements in the overall system efficiency are possible by optimizing the less efficient components. In particular, the fin's effectiveness can be improved in more than 5% after its shape is optimized, increments in the efficiency of the thermal energy storage of about 5.7% are possible when the mass is divided into four tanks, and solar receiver efficiencies up to 70% can be maintained for high operating temperatures (~ 1200°C) when a transparent insulation material is incorporated to the receiver. The results obtained in this dissertation indicate that concentrated solar systems using supercritical CO2 could be a viable alternative to satisfying energy needs in desert areas with scarce water and fossil fuel resources.
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Date Issued: 2016
Identifier: FSU_2016SP_Osorio_fsu_0071E_12890
Format: Thesis

Title: Gas Propagation in a Liquid Helium Cooled Vacuum Tube Following a Sudden Vacuum Loss.
Creator: Dhuley, Ram, Van Sciver, Steven W., Kopriva, David A., Hellstrom, Eric, Guo, Wei, Taira, Kunihiko, Florida State University, College of Engineering, Department of Mechanical...
Show moreDhuley, Ram, Van Sciver, Steven W., Kopriva, David A., Hellstrom, Eric, Guo, Wei, Taira, Kunihiko, Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: This dissertation describes the propagation of near atmospheric nitrogen gas that rushes into a liquid helium cooled vacuum tube after the tube suddenly loses vacuum. The loss-of-vacuum scenario resembles accidental venting of atmospheric air to the beam-line of a superconducting radio frequency particle accelerator and is investigated to understand how in the presence of condensation, the in-flowing air will propagate in such geometry. In a series of controlled experiments, room temperature...
Show moreThis dissertation describes the propagation of near atmospheric nitrogen gas that rushes into a liquid helium cooled vacuum tube after the tube suddenly loses vacuum. The loss-of-vacuum scenario resembles accidental venting of atmospheric air to the beam-line of a superconducting radio frequency particle accelerator and is investigated to understand how in the presence of condensation, the in-flowing air will propagate in such geometry. In a series of controlled experiments, room temperature nitrogen gas (a substitute for air) at a variety of mass flow rates was vented to a high vacuum tube immersed in a bath of liquid helium. Pressure probes and thermometers installed on the tube along its length measured respectively the tube pressure and tube wall temperature rise due to gas flooding and condensation. At high mass in-flow rates a gas front propagated down the vacuum tube but with a continuously decreasing speed. Regression analysis of the measured front arrival times indicates that the speed decreases nearly exponentially with the travel length. At low enough mass in-flow rates, no front propagated in the vacuum tube. Instead, the in-flowing gas steadily condensed over a short section of the tube near its entrance and the front appeared to `freeze-out'. An analytical expression is derived for gas front propagation speed in a vacuum tube in the presence of condensation. The analytical model qualitatively explains the front deceleration and flow freeze-out. The model is then simplified and supplemented with condensation heat/mass transfer data to again find the front to decelerate exponentially while going away from the tube entrance. Within the experimental and procedural uncertainty, the exponential decay length-scales obtained from the front arrival time regression and from the simplified model agree.
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Date Issued: 2016
Identifier: FSU_2016SP_Dhuley_fsu_0071E_13054
Format: Thesis

Title: On the Stability and Control of a Trailing Vortex.
Creator: Edstrand, Adam, Cattafesta, Louis N., Hussaini, M. Yousuff, Schmid, Peter J., Taira, Kunihiko, Oates, William S., Florida State University, College of Engineering, Department of...
Show moreEdstrand, Adam, Cattafesta, Louis N., Hussaini, M. Yousuff, Schmid, Peter J., Taira, Kunihiko, Oates, William S., Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: Trailing vortices are both a fundamental and practical problem of fluid mechanics. Fundamentally, they provide a canonical vortex flow that is pervasive in finite aspect ratio lifting bodies, practically producing many adverse effects across aeronautical and maritime applications. These adverse effects coupled with the broad range of applicability make their active control desirable; however, they remain robust to control efforts. Experimental baseline results provided an explanation of...
Show moreTrailing vortices are both a fundamental and practical problem of fluid mechanics. Fundamentally, they provide a canonical vortex flow that is pervasive in finite aspect ratio lifting bodies, practically producing many adverse effects across aeronautical and maritime applications. These adverse effects coupled with the broad range of applicability make their active control desirable; however, they remain robust to control efforts. Experimental baseline results provided an explanation of vortex wandering, the side-to-side motion often attributed to wind-tunnel unsteadiness or a vortex instability. We extracted the wandering motion and found striking similarities with the eigenmodes, growth rates, and frequencies from a stability analysis of the Batchelor vortex. After concluding that wandering is a result of a vortex instability, we applied control to the trailing vortex flow field through blowing from a slot at the wingtip. We experimentally obtained modest reductions in the metrics, but found the parameter space for optimization unwieldy. With the ultimate goal of designing control, we performed a physics-based stability analysis in the wake of a NACA0012 wing with an aspect ratio of 1.25 positioned at a geometric angle of attack of 5 degrees. Numerically computing the base flow at a chord Reynolds number of 1000, we perform a parallel temporal and spatial stability analysis three chords downstream of the trailing edge finding seven instabilities: three temporal, four spatial. The three temporal contain a wake instability, a vortex instability, and a mixed instability, which is a higher-order wake instability. The primary instability localized to the wake results from the two-dimensional wake, while the secondary instability is the mixed instability, containing higher-order spanwise structures in the wake. These instabilities imply that although it may be intuitive to place control at the wingtip, these results show that control may be more effective at the trailing edge, which would excite these instabilities that result with the eventual break up of the vortex. Further, by performing a wave-packet analysis, we found the wave packets contained directivity, coming inward toward the vortex above and below the wing, and traveling outward in the spanwise directions. We conjecture that this directivity can be translated to receptivity, with free-stream disturbances above and below the wing being more receptive than spanwise disturbances. With this, we provide two methods for instability excitation: utilizing control devices on the wing to excite near-field instabilities directly and utilizing free-stream disturbances to such as a speaker to excite near-field instabilities through receptivity.
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Date Issued: 2016
Identifier: FSU_2016SP_Edstrand_fsu_0071E_13141
Format: Thesis

Title: Processing and Characterization of Superconducting Solenoids Made of Bi-2212/Ag-Alloy Multifilament Round Wire for High Field Magnet Applications.
Creator: Chen, Peng, Larbalestier, D. (David), Trociewitz, Ulf Peter, Chiorescu, Irinel, Hellstrom, Eric, Guo, Wei, Florida State University, FAMU-FSU College of Engineering, Department...
Show moreChen, Peng, Larbalestier, D. (David), Trociewitz, Ulf Peter, Chiorescu, Irinel, Hellstrom, Eric, Guo, Wei, Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering
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Abstract/Description: As the only high temperature superconductor with round wire (RW) geometry, Bi2Sr2CaCu2O8+x (Bi-2212) superconducting wire has the advantages of being multi-filamentary, macroscopically isotropic and twistable. With overpressure (OP) processing techniques recently developed by our group at the National High Magnetic Field Laboratory (NHMFL), the engineering current density (Je) of Bi-2212 RW can be dramatically increased. For example, Je of more than 600 A/mm2 (4.2 K and 20 T) is achieved...
Show moreAs the only high temperature superconductor with round wire (RW) geometry, Bi2Sr2CaCu2O8+x (Bi-2212) superconducting wire has the advantages of being multi-filamentary, macroscopically isotropic and twistable. With overpressure (OP) processing techniques recently developed by our group at the National High Magnetic Field Laboratory (NHMFL), the engineering current density (Je) of Bi-2212 RW can be dramatically increased. For example, Je of more than 600 A/mm2 (4.2 K and 20 T) is achieved after 100 bar OP processing. With these intrinsically beneficial properties and recent processing progress, Bi-2212 RW has become very attractive for high field magnet applications, especially for nuclear magnetic resonance (NMR) magnets and accelerator magnets etc. This thesis summarizes my graduate study on Bi-2212 solenoids for high field and high homogeneity NMR magnet applications, which mainly includes performance study of Bi-2212 RW insulations, 1 bar and OP processing study of Bi-2212 solenoids, and development of superconducting joints between Bi-2212 RW conductors. Electrical insulation is one of the key components of Bi-2212 coils to provide sufficient electrical standoff within coil winding pack. A TiO2/polymer insulation offered by nGimat LLC was systematically investigated by differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), dielectric property measurements, and transport critical current (Ic) property measurements. About 29% of the insulation by weight is polymer. When the Bi-2212 wire is fully heat treated, this decomposes with slow heating to 400 °C in flowing O2. After the full reaction, we found that the TiO2 did not degrade the critical current properties, adhered well to the conductor, and provided a breakdown voltage of more than 100 V. A Bi-2212 RW wound solenoid coil was built using this insulation being offered by nGimat LLC. The coil resistance was constant through coil winding, polymer burn-off and full coil reaction. The coil was successfully tested at the NHMFL generating 33.8 T combined magnetic field in a 31.2 T background field. Multiple quenches occurred safely, which also illustrates that the insulation provided sufficient dielectric standoff. For Bi-2212 RW with a typical as-drawn diameter of 1.0-1.5 mm, this 15 µm thick insulation allows a very high coil packing factor of ~0.74, whereas earlier alumino-silicate braid insulation only allows packing factors of 0.38-0.48. In addition to the commercial TiO2/polymer insulation, we have also investigated sol-gel based ceramic coatings through collaboration with Harran University and another TiO2 based insulation coating at the NHMFL. Since Bi-2212 superconducting coils employ the Wind-and-React (W&R) technology, there are some potential issues in processing Bi-2212 coils, in particular for coils with a large thermal mass and dense oxide insulation coating. For this study, several Bi-2212 test solenoids with an outer diameter (OD) of about 90 mm were built and heat treated in 1 bar flowing oxygen with deadweights applied so as to simulate large coil packs. After the heat treatment (HT), coils were epoxy impregnated and cut. Winding pack was checked using SEM in terms of conductor geometry and insulation. Some samples were extracted to measure transport critical current Ic and critical temperature Tc. The results are very promising: test coils presented low creep behavior after standard partial melt HT under mechanical load, and no Ic degradation was found due to the application of mechanical load, and no inadequate oxygenation issue was seen for thick coils with ceramic coating on the wire. However, coils were partially electrically shorted after 1 bar HT under mechanical load, and we believe that increasing insulation coating thickness is necessary. In addition, several small solenoids were manufactured to study OP processing of Bi-2212 coils. The preliminary results indicate that there are some gaps between turns due to densification of wires (~4% wire diameter reduction) during 50-100 bar OP processing, and the diameter shrinking of conductors will potentially lead to coil sagging. So far, we have developed some methods to solve the issue of coil sagging, such as using flexible coil flange to allow smooth sagging of winding pack during OP processing. We have also investigated electrical joints between Bi-2212 RW conductors, which include resistive joints and superconducting joints. For resistive Bi-2212 joints, we evaluated conventional diffusion bonding method and soldering method. In general, the joints (with 42 mm joint length) resistances are below 200 nΩ at 4.2 K and magnetic fields up to 13.5 T, and the effect of magnetoresistance is clearly present. In addition to resistive joints, we successfully developed a superconducting joint between Bi-2212 RW conductors for persistent current mode (PCM) operations. The joint fabrication procedure is effective and practical, enabling Bi-2212 superconducting joints to be achieved during the standard Bi-2212 HT processing. First, the melting temperatures of Bi-2212 precursor mixtures with different amounts of Ag additions were investigated by DTA. Then, test joints were fabricated and heat treated in 1 bar flowing oxygen using the standard Bi-2212 HT schedule. The voltage-current (V-I) properties were measured using the conventional four-point method at 4.2 K in magnetic fields up to 14 T. A maximum supercurrent of ~850 A was achieved at 4.2 K and self-field. With the increase of external field, the supercurrent gradually decreased as expected, but a supercurrent of ~450 A was still presented at 4.2 K and 14 T. Compared with open-ended short samples with identical 1 bar Bi-2212 reaction, we found that the Ic properties of joints did not degrade. Meanwhile, microstructures of joints were examined by SEM, which clearly presented the formation of a Bi-2212 superconducting interface between two independent Bi-2212 RW conductors. Furthermore, a Bi-2212 RW closed-loop solenoid with a superconducting joint was fabricated and fully heat treated in 1 bar flowing oxygen. Using the field decay method, the joint resistance was estimated to be below 5×10-12 Ω at 4.2 K and self-field.
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Date Issued: 2016
Identifier: FSU_2016SP_Chen_fsu_0071E_13147
Format: Thesis

Title: Supersonic Impinging Jet Noise Reduction by Ground Plane Acoustic Treatment.
Creator: Vaca, Joaquin, Kumar, Rajan, Shih, Chiang, Oates, William S., Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: The flow field of supersonic impinging jets is known to be highly unsteady particularly for S/VTOL aircraft configuration. This can have adverse effects such as high noise levels, unsteady acoustic loads and sonic fatigue on the aircraft and surrounding structures, pavement erosion, ingestion of hot gases into the engine nacelle and lift loss of the aircraft. Jet noise from an aircraft has been a problem that significantly impacts aircraft operational procedures and adversely affects the...
Show moreThe flow field of supersonic impinging jets is known to be highly unsteady particularly for S/VTOL aircraft configuration. This can have adverse effects such as high noise levels, unsteady acoustic loads and sonic fatigue on the aircraft and surrounding structures, pavement erosion, ingestion of hot gases into the engine nacelle and lift loss of the aircraft. Jet noise from an aircraft has been a problem that significantly impacts aircraft operational procedures and adversely affects the health and safety of the personnel operating nearby and the communities surrounding airports / airbases and flight paths. In the present study, control of the highly resonant flow field associated with supersonic impinging jet by acoustic treatment at the impingement plane has been experimentally investigated. Measurements were made in the supersonic impinging jet facility at the Florida State University for a Mach 1.5 ideally expanded jet. Measurements included unsteady pressures on a surface plate near the nozzle exit and impingement plate, acoustics in the near field and beneath the impingement plane, and velocity field using particle image velocimetry. The passive control involves appropriately designed resonator panel to target discrete impinging tones and broadband noise. Results show that this technique is very effective in attenuating impinging tones and their harmonics in addition to significant broadband reduction.
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Date Issued: 2015
Identifier: FSU_migr_etd-9475
Format: Thesis

Title: High-Frequency, Resonance-Enhanced Microactuators with Active Structures for High-Speed Flow Control.
Creator: Kreth, Phillip Andrew, Alvi, Farrukh S., Locke, Bruce R., Shih, Chiang, Oates, William S., Florida State University, College of Engineering, Department of Mechanical Engineering
Abstract/Description: The need for actuators that are adaptable for use in a wide array of applications has been the motivation behind actuator development research over the past few years. Recent developments at the Advanced Aero-Propulsion Laboratory (AAPL) at Florida State University have produced a microactuator that uses the unsteadiness of a small-scale impinging jet to produce pulsed, supersonic microjets - this is referred to as the Resonance-Enhanced Microjet (REM) actuator. Prior studies on these...
Show moreThe need for actuators that are adaptable for use in a wide array of applications has been the motivation behind actuator development research over the past few years. Recent developments at the Advanced Aero-Propulsion Laboratory (AAPL) at Florida State University have produced a microactuator that uses the unsteadiness of a small-scale impinging jet to produce pulsed, supersonic microjets - this is referred to as the Resonance-Enhanced Microjet (REM) actuator. Prior studies on these actuators at AAPL have been been somewhat limited in that the actuator response has only been characterized through pressure/acoustic measurements and qualitative flow visualizations. Highly-magnified particle image velocimetry (PIV) measurements were performed to measure the velocity fields of both a 1 mm underexpanded jet and an REM actuator. The results demonstrate that this type of microactuator is capable of producing pulsed, supersonic microjets that have velocities of approximately 400 m/s that are sustained for significant portions of their cycles (> 60 %). These are the first direct velocity measurements of these flowfields, and they allow for a greater understanding of the flow physics associated with this microactuator. The previous studies on the REM actuators have shown that the microactuator volume is among the principal parameters in determining the actuator's maximum-amplitude frequency component. In order to use this actuator in a closed-loop, feedback control system, a modified design that incorporates smart materials is studied. The smart materials (specifically piezoelectric ceramic stack actuators) have been implemented into the microactuator to actively change its geometry, thus permitting controllable changes in the microactuator's resonant frequency. The distinct feature of this design is that the smart materials are not used to produce the primary perturbation or flow from the actuator (which has in the past limited the control authority of other designs) but to change its dynamic properties. Various static and dynamic control inputs to the piezo-stacks illustrate that the actuator's resonant frequency can be modulated by a few hundred Hertz at very fast rates (up to 1 kHz or more). These frequency modulation capabilities allow for off-design frequencies to be present in the actuator's output, thereby increasing its range of potential flow control applications. A series of closed-loop control demonstrations clearly show the ability of this actuator to track and produce outputs at specified frequencies. The robustness of this control technique was also demonstrated. By combining the REM actuator concept with the precision and control authority of smart materials, the new actuator system (known as the SmartREM actuator) is shown to produce supersonic, pulsing microjets whose frequency can be controlled actively in a closed-loop manner. Three different design possibilities are developed and characterized in this study. An optimal configuration was identified for cavity flow control experiments in both sub- and supersonic freestream conditions (M = 0.4 - 0.7 and M = 1.5). The actuator was designed such that its frequency would lie within the range of the predicted cavity oscillations. The actuator's performance was evaluated in its three modes of operations: pulsed (REM mode), active pulsed (SmartREM mode), and steady. It was found that when the actuator operates in its pulsed modes, the amplitude of the dominant peak is reduced by as much as 6 dB. The high-frequency broadband levels and overall sound pressure levels (OASPLs) are reduced with control as well (by about 3 dB). Operating the actuator in its steady mode at very high pressures provides the most effective results. The dominant peaks were completely eliminated (amplitudes reduced by over 25 dB), and the reductions in the OASPLs exceeded 10 dB.
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Date Issued: 2015
Identifier: FSU_migr_etd-9635
Format: Thesis

Title: A Graph Based Approach to Nonlinear Model Predictive Control with Application to Combustion Control and Flow Control.
Creator: Reese, Brandon M., Collins, E. (Emmanuel), Alvi, Farrukh S., Foo, Simon Y., Cattafesta, Louis N., Oates, William S., Florida State University, College of Engineering, Department...
Show moreReese, Brandon M., Collins, E. (Emmanuel), Alvi, Farrukh S., Foo, Simon Y., Cattafesta, Louis N., Oates, William S., Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: Systems with a priori unknown, and time-varying dynamic behavior pose a significant challenge in the field of Nonlinear Model Predictive Control (NMPC). When both the identification of the nonlinear system and the optimization of control inputs are done robustly and efficiently, NMPC may be applied to control such systems. This dissertation presents a novel method for adaptive NMPC, called Adaptive Sampling Based Model Predictive Control (SBMPC), that combines a radial basis function neural...
Show moreSystems with a priori unknown, and time-varying dynamic behavior pose a significant challenge in the field of Nonlinear Model Predictive Control (NMPC). When both the identification of the nonlinear system and the optimization of control inputs are done robustly and efficiently, NMPC may be applied to control such systems. This dissertation presents a novel method for adaptive NMPC, called Adaptive Sampling Based Model Predictive Control (SBMPC), that combines a radial basis function neural network identification algorithm with a nonlinear optimization method based on graph search. Unlike other NMPC methods, it does not rely on linearizing the system or gradient based optimization. Instead, it discretizes the input space to the model via pseudo-random sampling and feeds the sampled inputs through the nonlinear model, producing a searchable graph. An optimal path is found using an efficient graph search method. Adaptive SBMPC is used in simulation to identify and control a simple plant with clearly visualized nonlinear dynamics. In these simulations, both fixed and time-varying dynamic systems are considered. Next, a power plant combustion simulation demonstrates successful control of a more realistic Multiple-Input Multiple-Output system. The simulated results are compared with an adaptive version of Neural GPC, an existing NMPC algorithm based on Netwon-Raphson optimization and a back propagation neural network model. When the cost function exhibits many local minima, Adaptive SBMPC is successful in finding a globally optimal solution while Neural GPC converges to a solution that is only locally optimal. Finally, an application to flow separation control is presented with experimental wind tunnel results. These results demonstrate real time feasibility, as the control updates are computed at 100 Hz, and highlight the robustness of Adaptive SBMPC to plant changes and the ability to adapt online. The experiments demonstrate separation control for a NACA 0025 airfoil with Reynolds Numbers ranging from 90,000 to 150,000 for both fixed and pitching (.33 deg/s) angles of attack.
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Date Issued: 2015
Identifier: FSU_migr_etd-9435
Format: Thesis

Title: Identification of the Inertial Parameters of Manipulator Payloads.
Creator: Reyes, Ryan-David, Department of Electrical and Computer Engineering
Abstract/Description: Momentum based motion planning allows small and lightweight manipulators to lift loads that exceed their rated load capacity. One such planner, Sampling Based Model Predictive Optimization (SBMPO) developed at the Center for Intelligent Systems, Control, and Robotics (CISCOR), uses dynamic and kinematic models to produce trajectories that take advantage of momentum. However, the inertial parameters of the payload must be known before the trajectory can be generated. This research utilizes a...
Show moreMomentum based motion planning allows small and lightweight manipulators to lift loads that exceed their rated load capacity. One such planner, Sampling Based Model Predictive Optimization (SBMPO) developed at the Center for Intelligent Systems, Control, and Robotics (CISCOR), uses dynamic and kinematic models to produce trajectories that take advantage of momentum. However, the inertial parameters of the payload must be known before the trajectory can be generated. This research utilizes a method based on least squares techniques for determining the inertial parameters of a manipulator payload. It is applied specifically to a two degree of freedom manipulator. A set of exciting trajectories, i.e., trajectories that sufficiently excite the manipulator dynamics, in task space will be commanded to the system. Inverse kinematics are then used to determine the desired angle, angular velocity, and angular acceleration for the manipulator joints. Using the sampled torque, joint position, velocity, and acceleration data, the least squares technique produces an estimate of the inertial parameters of the payload. This paper focuses on determining which trajectories produce sufficient excitation so that an adequate estimate can be obtained.
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Date Issued: 2014
Identifier: FSU_migr_uhm-0418
Format: Thesis

Title: Design of a Biologically Inspired Jumping Mechanism for a Dynamic Running Platform.
Creator: Carbiener, Charles, Department of Mechanical Engineering
Abstract/Description: Many animals are capable of jumping from a running gait. This allows them to quickly overcome a large range of obstacles. A robotic platform capable of running jumps will benefit similarly, and see a great enhancement to its mobility. This thesis presents the design, simulation and preliminary validation of a robotic leg capable of both running and jumping. Two reduced order running models are introduced to investigate the dynamics of running and jumping. These models are used to demonstrate...
Show moreMany animals are capable of jumping from a running gait. This allows them to quickly overcome a large range of obstacles. A robotic platform capable of running jumps will benefit similarly, and see a great enhancement to its mobility. This thesis presents the design, simulation and preliminary validation of a robotic leg capable of both running and jumping. Two reduced order running models are introduced to investigate the dynamics of running and jumping. These models are used to demonstrate that a platform can control its trajectory by changing the timing of its jump and to guide the design of a functional prototype. This prototype functions by storing energy by deforming a compliant element, which can then be released into a jump when needed. The prototype was built and several proof of concept tests were performed to show the capabilities of this prototype.
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Date Issued: 2014
Identifier: FSU_migr_uhm-0301
Format: Thesis

Title: Photomechanical Responses in Polymerized Azobenzene and Application to Heliostats.
Creator: Roberts, Dennice, Department of Physics
Abstract/Description: The search for viable forms of alternative energy has been a topic of recent research, and harvesting of solar energy has already been realized in various forms. Certain compounds have been shown to have visible physical responses when hit with light, transforming optical energy into motion. This project aims to better characterize properties of azobenzene, one such polymeric photomechanical actuator by considering it under various conditions of incident LED light. While much previous...
Show moreThe search for viable forms of alternative energy has been a topic of recent research, and harvesting of solar energy has already been realized in various forms. Certain compounds have been shown to have visible physical responses when hit with light, transforming optical energy into motion. This project aims to better characterize properties of azobenzene, one such polymeric photomechanical actuator by considering it under various conditions of incident LED light. While much previous research has been done on azobenzene polymerized in a polyacrylate, this project holds its focus on an azobenzene-doped polyimide compound. It also attempts to understand the role this smart material may play in solar heliostats. The movement of these apparati is usually controlled by electromagnetic motors, but could instead be moved using azobenzene as a photon-powered motor that does work on the polymer network.
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Date Issued: 2014
Identifier: FSU_migr_uhm-0367
Format: Thesis

Title: Design and Characterization of a Dielectric Elastomer Based Variable Stiffness Mechanism for Implementation onto a Dynamic Running Robot.
Creator: Newton, Jason, Clark, Jonathan, Oates, William, Hollis, Patrick, Department of Mechanical Engineering, Florida State University
Abstract/Description: Biological systems show a reliance upon their capability to adapt limb stiffness as a means to achieve dynamically similar locomotion over a wide range of terrains. The versatility of robotic platforms falls short in comparison to their biological counterparts. One possible method to enhance the performance of these systems is to integrate a variable stiffness mechanism into the locomotive structure to aid in their adaptability. To date, many variable stiffness mechanisms have been designed,...
Show moreBiological systems show a reliance upon their capability to adapt limb stiffness as a means to achieve dynamically similar locomotion over a wide range of terrains. The versatility of robotic platforms falls short in comparison to their biological counterparts. One possible method to enhance the performance of these systems is to integrate a variable stiffness mechanism into the locomotive structure to aid in their adaptability. To date, many variable stiffness mechanisms have been designed, but they have multiple drawbacks. The current mechanisms are typically too slow to achieve rapid adaptations during dynamic locomotion or too large for implementation onto smaller platforms. It is desirable to have a variable stiffness mechanism that is able to achieve a large reduction in stiffness in the minimal amount of time. This work focuses on the development process of a dielectric elastomer based variable stiffness mechanism as a replacement for traditional springs on a legged hexapedal robot. A simulation is developed assessing the stability benefits of an ideal variable stiffness mechanism actuated over the period of a single stride during dynamic locomotion. The design process is detailed and the characterization of the mechanism in terms of its magnitude for stiffness reduction, transient response to stimuli, and implementability is presented. The newly developed system shows up to an order of magnitude reduction in stiffness at an actuation frequency approximated at 10 Hz. The system is implemented onto an adapted version of the dynamic running robot, iSprawl, and its performance is characterized with respect to forward velocity. Reliability issues in the current manufacturing process pose a potential problem, but new methods are proposed to increase durability and repeatability of the mechanism. Finally, the next generation design for implementation onto a new platform is presented.
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Date Issued: 2014
Identifier: FSU_migr_etd-9058
Format: Thesis

Title: Transient Heat Transfer to Helium II Due to a Sudden Loss of Insulating Vacuum.
Creator: Bosque, Ernesto, Van Sciver, Steven, Kopriva, David, Ordoñez, Juan, Clark, Jonathan, Department of Mechanical Engineering, Florida State University
Abstract/Description: Rapid heat deposition is a natural consequence of an insulating vacuum jacket failure around a He II-cooled system. This loss of vacuum is often referred to as the worst-case scenario, as it seriously endangers its surroundings and the low temperature equipment cooled within. In the case of a vacuum break, air floods into the vacuum jacket, impinging on the inner vacuum wall. The air carries with it a significant amount of energy (~500 kJ/kg) that is ultimately transferred to the He II...
Show moreRapid heat deposition is a natural consequence of an insulating vacuum jacket failure around a He II-cooled system. This loss of vacuum is often referred to as the worst-case scenario, as it seriously endangers its surroundings and the low temperature equipment cooled within. In the case of a vacuum break, air floods into the vacuum jacket, impinging on the inner vacuum wall. The air carries with it a significant amount of energy (~500 kJ/kg) that is ultimately transferred to the He II coolant. Given large magnitudes, the heat flux results in rapid pressurization due to the expansion of the helium as it boils to its vapor phase. An experimental rig has been designed, built, and successfully operated to simulate such a sudden loss of insulating vacuum incident confined to one-dimension in space. The rig consists of an evacuated tube that dead-ends to a He II-cooled disk, beneath which is a column of He II near 1.8 K, open to its bath. A wide range of mass flow rates are studied for warm gas flooding into the evacuated tube, causing the gas to cryodeposit and transfer its internal energy through the disk and to the He II. Thermometry in the disk and axially through the He II column is used to quantify the heat transport generated by the cryodeposition process. In general, it is found that the heat flux to the He II is indeed limited by peak heat flux theory. It is further confirmed that noisy film boiling, though mechanically violent, reduces the heat transfer to the He II. The cryodeposition behavior of warm gas onto a He II-cooled surface is also shown to be somewhat stochastic. In summary, an accurate conceptual model is developed to fundamentally describe and predict the coupled mass and heat transport phenomena that result after such a vacuum failure.
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Date Issued: 2014
Identifier: FSU_migr_etd-8734
Format: Thesis

Title: He II Heat Transfer Through Random Packed Spheres.
Creator: Vanderlaan, Mark, Van Sciver, Steven, Brooks, James, Oates, William, Shih, Chiang, Department of Mechanical Engineering, Florida State University
Abstract/Description: Superfluid helium (He II) contained in porous media is examined. In particular, heat transfer experiments were performed on He II contained in random packs of uniform size polyethylene spheres. Measured results include the steady state temperature and pressure drops across packs of spheres (35 micron, 49 micron, and 98 micron diameter) and the associated steady, step, and pulse heat inputs. Bath temperatures range from 1.6 K to 2.1 K to help grasp the superfluid effects. Laminar, turbulent,...
Show moreSuperfluid helium (He II) contained in porous media is examined. In particular, heat transfer experiments were performed on He II contained in random packs of uniform size polyethylene spheres. Measured results include the steady state temperature and pressure drops across packs of spheres (35 micron, 49 micron, and 98 micron diameter) and the associated steady, step, and pulse heat inputs. Bath temperatures range from 1.6 K to 2.1 K to help grasp the superfluid effects. Laminar, turbulent, and transitional fluid flow regimes are examined. Turbulent results are fitted to an empirically derived turbulent He II heat flow in a channel equation with an added tortuosity (extra length traveled) term that accounts for the porous media. An average tortuosity of 1.33 ± 0.07 was obtained, which is in good agreement with the values of 1.36 - 1.41 concluded from published work on classical fluid pressure drop across random packed spheres. Laminar permeability and shape factor results are compared to past studies of He II in porous media and in channel flows. The average critical heat flux, which describes the onset of turbulence, is predicted to be 0.19 W cm-2. The onset of turbulence is determined through a critical heat flux from which a critical Reynolds number is formulated, but does not describe He II turbulence in the normal fluid component. Other proposed He II "Reynolds numbers" are examined. The addition of the laminar and turbulent heat flow equations into a unifying prediction fits the transition regime data within 25 %. Transient temperatures compare favorably to a one-dimensional numerical solution that considers a variable Gorter-Mellink exponent and a piece-wise determination of the heat flux. Turbulent pressure drop results are fitted with empirically derived friction factors. The laminar permeability and equivalent channel shape factor derived from the pressure drop are compared the permeability and shape factor obtained from the temperature drop. Results from the pressure drop experiments are more accurate than temperature drop experiments due to reduced measurement errors with the pressure transducer. Turbulent theories considering only dynamic pressure losses in the normal fluid yield the most consistent friction factors. The addition of the laminar and turbulent heat flow equations into a unifying prediction fits all regimes to within 10 %.
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Date Issued: 2014
Identifier: FSU_migr_etd-8905
Format: Thesis

Title: Unsteady Aerodynamics of Maneuvering Wings: Numerical Simulations of Vortex Dynamics and Force Modeling.
Creator: Jantzen, Ryan T., Taira, Kunihiko, Alvi, Farrukh, Oates, William, Department of Mechanical Engineering, Florida State University
Abstract/Description: Vortex dynamics of wakes generated by rectangular aspect-ratio 2 and 4 and two-dimensional pitching flat plates in free stream are examined with direct numerical simulation and water tunnel experiments. Evolution of wake vortices comprised of tip, leading-edge and trailing-edge vortices is compared with force history for a range of pitch rates. The plate pivots about its leading edge over a range of reduced frequencies. Computations have reasonable agreement with experiments, despite in some...
Show moreVortex dynamics of wakes generated by rectangular aspect-ratio 2 and 4 and two-dimensional pitching flat plates in free stream are examined with direct numerical simulation and water tunnel experiments. Evolution of wake vortices comprised of tip, leading-edge and trailing-edge vortices is compared with force history for a range of pitch rates. The plate pivots about its leading edge over a range of reduced frequencies. Computations have reasonable agreement with experiments, despite in some cases large differences in Reynolds number. Computations show that the tip effects are confined initially near the wing tips, but begin to strongly affect the leading-edge vortex as the motion of the plate proceeds, with concomitant effects on lift and drag history. Scaling relations based on reduced frequency are shown to collapse aerodynamic force history for the various pitch rates. We also report on the development of an aerodynamic force model for a flat-plate wing undergoing unsteady motions of surging, pitching, and the combination thereof in two-dimensional flow. This investigation aims to extend the conventional quasi-steady aerodynamic theory to account for the influence of large-scale vortices generated from the massively separated flow at high angles of attack. A data set compiled from direct numerical simulation is used to develop the force model. Particular focus is placed on examining the influence of large-amplitude wing motion on the unsteady aerodynamics force. This is especially important since the resulting circulatory component of force is significant in size and is nonlinearly related to the flow field causing deviation from conventional aerodynamic theories. The present force model is constructed to predict the aerodynamic force on the body for the duration of the wing motion.
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Date Issued: 2014
Identifier: FSU_migr_etd-8815
Format: Thesis

Title: On the Properties and Mechanisms of Microjet Arrays in Crossflow for the Control of Flow Separation.
Creator: Fernandez, Erik J., Alvi, Farrukh S., Zheng, Jianping P., Taira, Kunihiko, Kumar, Rajan, Collins, E. (Emmanuel), Florida State University, College of Engineering, Department of...
Show moreFernandez, Erik J., Alvi, Farrukh S., Zheng, Jianping P., Taira, Kunihiko, Kumar, Rajan, Collins, E. (Emmanuel), Florida State University, College of Engineering, Department of Mechanical Engineering
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Abstract/Description: By utilizing passive and active methods of flow control, the aerodynamic performance of external and internal components can be greatly improved. Recently however, the benefits of applying active flow control methods to turbomachinery components for improved fuel efficiency, reduced engine size, and greater operational envelope has sparked a renewed interest in some of these flow control techniques. The more attractive of these, is active control in the form of jets in cross flow. With their...
Show moreBy utilizing passive and active methods of flow control, the aerodynamic performance of external and internal components can be greatly improved. Recently however, the benefits of applying active flow control methods to turbomachinery components for improved fuel efficiency, reduced engine size, and greater operational envelope has sparked a renewed interest in some of these flow control techniques. The more attractive of these, is active control in the form of jets in cross flow. With their ability to be turned on and off, as well as their negligible effect on drag when not being actuated, they are well suited for applications such as compressor and turbine blades, engine inlet diffusers, internal engine passages, and general external aerodynamics. This study consists of two parts. The first is the application of active control on a low-pressure turbine (LPT) cascade to determine the effectiveness of microjet actuators on flow separation at relatively low speeds. The second study, motivated by the first, involves a parametric study on a more canonical model to examine the effects of various microjet parameters on the efficacy of separation control and to provide a better understanding of the relevant flow physics governing this control approach. With data obtained from velocity measurements across the wide parametric range, correlations for the growth of the counter-rotating vortex pairs generated by these actuators are deduced. From the information and models obtained throughout the study, basic suggestions for microjet actuator design are presented.
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Date Issued: 2014
Identifier: FSU_migr_etd-9174
Format: Thesis

Title: Rollover Procedures for Crashworthiness Assessment of Paratransit Bus Structures.
Creator: Gepner, Bronislaw Dominik, Wekezer, Jerry W., Jung, Sungmoon, Liang, Zhiyong Richard, Mtenga, Primus V., Plewa, Tomasz, Florida State University, FAMU-FSU College of Engineering...
Show moreGepner, Bronislaw Dominik, Wekezer, Jerry W., Jung, Sungmoon, Liang, Zhiyong Richard, Mtenga, Primus V., Plewa, Tomasz, Florida State University, FAMU-FSU College of Engineering, Department of Civil and Environmental Engineering
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Abstract/Description: The following dissertation presents the initial stages of the development of the new rollover safety assessment protocol developed for paratransit buses. Each year, the State of Florida purchases over 300 paratransit buses. In 2011, the purchased buses came with over 40 different floor/wheelbase/chassis configurations. Such variety of purchased vehicles gives the ordering agencies a flexibility of ordering vehicles optimized for desired purpose, but also creates a challenge for the rollover...
Show moreThe following dissertation presents the initial stages of the development of the new rollover safety assessment protocol developed for paratransit buses. Each year, the State of Florida purchases over 300 paratransit buses. In 2011, the purchased buses came with over 40 different floor/wheelbase/chassis configurations. Such variety of purchased vehicles gives the ordering agencies a flexibility of ordering vehicles optimized for desired purpose, but also creates a challenge for the rollover safety assessment procedures. Currently, there are two standards available to be used for rollover crashworthiness assessment of buses, the FMVSS 220 standard and the UN-ECE Regulation 66. The FMVSS 220 is commonly used in the United States to evaluate rollover crashworthiness of wide variety of buses. Its quasi-static nature offers an attractive, easy to perform test that provides good repeatability of results. Nevertheless, due to the nature of applied load, this procedure may not be the best choice for evaluating the dynamic behavior of a bus during a rollover accident. In contrast, the UN-ECE Regulation 66 employs a full scale, dynamic rollover test to examine response of buses in rollover accidents. The dynamic rollover, which forms the basis of the ECE-R66 approval procedure closely resembles the real world rollover accident and this regulation has been adopted by over 40 countries in the world. However, the dynamic nature of this test makes it expensive, time consuming and difficult to perform. This situation calls for an update of an approval procedure, in order to test the purchased buses within the available time and budget. The initial development of the new assessment protocol, the Equivalent Rollover Testing (ERT) procedure, was carried out in this dissertation. The ERT procedure is conceived as an alternative approval method for the experimental or virtual full scale rollover testing. The new protocol was developed based on collected experimental experience, extensive numerical studies and theoretical considerations. The ERT procedure establishes a set of experimental tests, on the components of bus structure, that if satisfied give a high level of confidence that the tested bus will pass the requirements of the ECE-R66 rollover procedure. The proposed ERT procedure is further tested through the parametric studies on five detailed finite element models of paratransit buses. The models, developed in the Crashworthiness and Impact Analysis Laboratory (CIAL), cover a wide range of buses, from small 138 in to a large 255 in wheelbase configurations. Through the modifications of structural components of each of the buses, a set of 132 bus designs and corresponding 132 rollover tests was established. Each of the developed buses was also subjected to the provisions of the ERT procedure. The comparison of results showed that ERT procedure presents a conservative approach to paratransit bus safety evaluation. Out of all 132 test cases there was not a single bus that passed the provisions of the ERT procedure, but has failed the full scale ECE-R66 rollover test. The proposed ERT procedure, complemented by future validation experimental study presents a promising alternative for the paratransit bus rollover safety evaluation.
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Date Issued: 2014
Identifier: FSU_migr_etd-9176
Format: Thesis

Title: An Additive Manufacturing Acrylic for Use in the 32 Tesla All Superconducting Magnet.
Creator: Johnson, Zachary, Hellstrom, Eric, Liang, Zhiyong Richard, Oates, William S., Florida State University, The Graduate School, Program in Materials Science
Abstract/Description: The National High Magnetic Field Laboratory is building a world record all superconducting magnet known as the "32T". It requires many thousands of parts, but in particular one kind is unusually expensive to manufacture, called "heater lead covers". These parts are traditionally made out of a glass filled epoxy known as G-10, and conventionally machined. The machining is the expensive portion, as there are many tight tolerance details. The proposal in this paper is to change the material and...
Show moreThe National High Magnetic Field Laboratory is building a world record all superconducting magnet known as the "32T". It requires many thousands of parts, but in particular one kind is unusually expensive to manufacture, called "heater lead covers". These parts are traditionally made out of a glass filled epoxy known as G-10, and conventionally machined. The machining is the expensive portion, as there are many tight tolerance details. The proposal in this paper is to change the material and manufacturing method to additive manufacturing with the material called "RGD 430". The cost per part with traditional machining is approximately $1,500 each. The cost per part with additive manufacturing of RGD 430 is approximately $32.5 each. There will be at least 14 of this style of part on the completed 32T project. Thus the total cost for the project will be reduced from $21,000 to $455, a 98% cost savings. The additive manufacturing also allows the machine designers to expand the dimensions of the part to any shape possible. Through testing of the material it was found to follow the common polymer characteristics. Its linear elastic modulus at cryogenic temperatures approached 10 GPa. The yield strength was always over 100 MPa, when not damaged. The fracture mechanism was repeatable, and brittle in cryogenic environments. The geometric tolerancing of the additive manufacturing process are, as expected extremely precise. The final tolerances for dimensions in the profile of the printer are more precise than +/- 0.10mm. The final tolerances for dimensions in the thickness of the printer are more precise than +/-0.25mm. Before utilizing the material, there should be a few additional tests run on it to ensure it will work in-situ. Those tests are outside the scope of this thesis.
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Date Issued: 2014
Identifier: FSU_migr_etd-9194
Format: Thesis

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