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- Title
- Characterization of Microfluidic Channels for Biodiagnostics.
- Creator
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Zwolinski, Andrew Michael, Haik, Yousef, Chen, Ching-Jen, Shih, Chiang, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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Characterization of fluid with suspended nanoparticles in microchannels has been studied as a part of a microfluidic based acute myocardial infarction (AMI) detection device. The AMI detection process uses heat stabilized human serum albumin (HSA) magnetic microspheres and specific antibodies to create a magnetic immunoassay used in the detection of AMI. Microanalysis systems have several advantages over conventional analysis systems due to their sensitivity, reliability and the amount of...
Show moreCharacterization of fluid with suspended nanoparticles in microchannels has been studied as a part of a microfluidic based acute myocardial infarction (AMI) detection device. The AMI detection process uses heat stabilized human serum albumin (HSA) magnetic microspheres and specific antibodies to create a magnetic immunoassay used in the detection of AMI. Microanalysis systems have several advantages over conventional analysis systems due to their sensitivity, reliability and the amount of anlaytes needed for the test. The microchannels used in this work were fabricated at Sandia National Laboratories (SNL) using a SwIFT⢠microfabrication surface micromaching process. Micro channels made of Poly(dimethylsiloxane)-glass (PDMS-glass) designed and fabricated at the Department of Chemistry at the Florida State University were also used in this work. The SwIFT⢠microchannels had dimensions of 6µm in height, 20µm in width and 200µm in length where as the PDMS-glass microchannels had dimensions of 40µm in height, 200µm wide and 13mm in length. Characterization of the microchannels was accomplished using a variety of techniques. The first method used to characterize the microchannels was to used a head pressure-flow set up to determine the pressure and flow characteristics of the SwIFT⢠microchannels with the different fluids that the biodiagnostic process calls for, with average mass flow rate being 1.9x10-2 µg/s and Reynolds number of 1.45 at a pressure of 23kPa for a typical channel, these values approach the upper limit of the work accomplished. Since the HSA microspheres, 1µm in diameter and less, play a critical role in the detection protocol their compatibility to the SwIFT⢠microchannels was investigated. Results showed the HSA microspheres agglomerated and adsorbed to the walls of the channels. Fluorescence correlation spectroscopy (FCS) was attempted on the SwIFT⢠microchannels with 200nm and 40nm beads and the same conclusion of agglomeration and adsorption was reached which made these channels not suitable for adaptation in the microanaylsis system considered for AMI detection. PDMS-glass microchannels head pressure-flow rates were also investigated showing an average mass flow rate of 1.76x10-1µg/s and a Reynolds number of 1.03 at a pressure of 4.5kPa. FCS was preformed on these channels successfully without any signs of agglomeration, though some adsorption of the beads to the walls of the channel was evident. FCS measured max velocity was equal to approximately 6.6 cm/s. Thus it is concluded that microchannels of similar sizes of the PDMS-glass will be needed in the microanalysis system that is being developed to detect for AMI markers.
Show less - Date Issued
- 2004
- Identifier
- FSU_migr_etd-0470
- Format
- Thesis
- Title
- Experimental Investigation of Supersonic Cavity Flows and Their Control.
- Creator
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Zhuang, Ning, Alvi, Farrukh S., Shih, Chiang, Tam, Christopher, Annaswamy, Anuradha, Collins, Emmanuel G., Department of Mechanical Engineering, Florida State University
- Abstract/Description
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The study of supersonic cavity flows is of interest both from fundamental fluid dynamics and practical perspectives. The complex nature of this flowfield, consisting of compressible shear layers, compression/expansion waves, and fluid-acoustic interactions, makes it a rich problem to study. A detailed experimental study of supersonic flow (M=1.5 to 2) over a range of three-dimensional rectangular cavities (L/D=1 to 5.2) was conducted. The measurements included unsteady surface pressure...
Show moreThe study of supersonic cavity flows is of interest both from fundamental fluid dynamics and practical perspectives. The complex nature of this flowfield, consisting of compressible shear layers, compression/expansion waves, and fluid-acoustic interactions, makes it a rich problem to study. A detailed experimental study of supersonic flow (M=1.5 to 2) over a range of three-dimensional rectangular cavities (L/D=1 to 5.2) was conducted. The measurements included unsteady surface pressure measurements, particle image velocimetry, and flow visualization using shadowgraph and schlieren. Large-scale structures in the shear layer and a large recirculation zone in the cavity was observed. Spatial and temporal mode switching was also observed, the nature being different for short and long cavities. The shear layer characteristics of the two cavities are very different in term of curvature and growth. Supersonic microjets were used at the leading edge of the cavities to suppress the resonance in the flow. With a minimal mass flux (0.15%), the activation of microjets led to a large reduction in cavity tones (20 dB) and overall sound pressure levels (9dB). In addition, the microjet injection enhanced the shear layer mixing and reduced the velocity fluctuation in the cavities. The significant reductions together with the low mass flux requirements make this a potentially viable technique for full-scale, practical applications.
Show less - Date Issued
- 2007
- Identifier
- FSU_migr_etd-0508
- Format
- Thesis
- Title
- A Comparison of Pole Assignment & LQR Design Methods for Multivariable Control for Statcom.
- Creator
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Xing, Liqun, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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The static synchronous compensator (STATCOM) is increasingly popular in power system application. In general, power factor and stability of the utility system can be improved by STATCOM. Specifically, STATCOM can stabilize a given node voltage and compensate for the power factors of equipment serviced by that node. The dynamic performance of STATCOM is critical to these performance and stability function. STATCOM is a multiple input and multiple output system (MIMO), which can be presented by...
Show moreThe static synchronous compensator (STATCOM) is increasingly popular in power system application. In general, power factor and stability of the utility system can be improved by STATCOM. Specifically, STATCOM can stabilize a given node voltage and compensate for the power factors of equipment serviced by that node. The dynamic performance of STATCOM is critical to these performance and stability function. STATCOM is a multiple input and multiple output system (MIMO), which can be presented by a mathematic model. Recently, full MIMO state feedback by pole assignment has been shown to be an improvement over classical PI control. In this thesis, an optimal linear quadratic regulator (LQR) design is a compared to the pole assignment design for transient dynamic performance of STATCOM. It was found that LQR controllers do not offer significant performance improvement to pole assignment. However, as a design method the determination of state feedback gains is easier using the LQR method
Show less - Date Issued
- 2003
- Identifier
- FSU_migr_etd-0413
- Format
- Thesis
- Title
- Study of the Magnetic Field Dependence of the Critical Current of Bi2Sr2Cacu2O8+X and (Bi,Pb)2Sr2Ca2Cu3O10+X Superconducting Tapes.
- Creator
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Xu, Bin, Schwartz, Justin, Hruda, Simone Peterson, Luongo, Cesar, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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The magnetic field dependence of critical currents are studied in Bi2Sr2CaCu2O8+x and (Bi,Pb)2Sr2Ca2Cu3O10+x multifilamentary superconducting tapes. The critical current was measured in the magnetic fields up to 5 T, at 4.2 K, with several orientations of the applied magnetic field relative to the tape. The critical current is determined by the normal (c-axis) component of the applied magnetic field over a wide range. At low magnetic fields, the field dependence of the critical current is...
Show moreThe magnetic field dependence of critical currents are studied in Bi2Sr2CaCu2O8+x and (Bi,Pb)2Sr2Ca2Cu3O10+x multifilamentary superconducting tapes. The critical current was measured in the magnetic fields up to 5 T, at 4.2 K, with several orientations of the applied magnetic field relative to the tape. The critical current is determined by the normal (c-axis) component of the applied magnetic field over a wide range. At low magnetic fields, the field dependence of the critical current is mainly dominated by weak-links, while at the higher fields it is determined by the strong-links current path limited by intragranular flux pinning. Two-dimensional behavior of the critical current in Bi2Sr2CaCu2O8+x and (Bi,Pb)2Sr2Ca2Cu3O10+x multifilamentary tapes is observed. From 2D behavior it is possible to calculate the average misalignment angle of the grains from critical current measurements in a magnetic field oriented perpendicular and parallel to the tape plane. The results are compared with a reported model that describes the angular dependence of critical currents [*]. The model is based on a Gaussian distribution of the misalignment angles of the grains. With this model it is possible to calculate the standard deviation of the misalignment angle of the grains from critical current measurements in a magnetic field oriented perpendicular and parallel to the tape plane. This model is confirmed experimentally. The angular dependence of the critical current of the measured tapes can be described at 4.2 K in the region between 0 and 5 T by using a standard deviation. [*] O. van der Meer, B. ten Haken, and H.H.J. ten Kate, "A model to describe the angular dependence of the critical current in a Bi-2223/Ag superconducting tape," Physica C 357-360, 1174 (2001).
Show less - Date Issued
- 2004
- Identifier
- FSU_migr_etd-0415
- Format
- Thesis
- Title
- Velocity Field Measurements of He II Forced Flow Using the Particle Image Velocimetry Technique.
- Creator
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Xu, Ting, Sciver, Steven W. Van, Brooks, James S., Luongo, Cesar A., Schwartz, Justin, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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We report measurements of the velocity fields in He II forced flow obtained by the Particle Image Velocimetry (PIV) technique, a technique which uses micron scale tracer particles to track the flow. We demonstrate that the micron size solid deuterium particles are the best choice for tracing He II forced flow in a horizontal channel. A novel particle seeding device has been developed to form micron size solid hydrogen isotope tracer particles directly within a He II flow. The tracking...
Show moreWe report measurements of the velocity fields in He II forced flow obtained by the Particle Image Velocimetry (PIV) technique, a technique which uses micron scale tracer particles to track the flow. We demonstrate that the micron size solid deuterium particles are the best choice for tracing He II forced flow in a horizontal channel. A novel particle seeding device has been developed to form micron size solid hydrogen isotope tracer particles directly within a He II flow. The tracking mechanism and the fidelity of these particles have been examined and are discussed herein. He II forced flows up to 287 mm/s are created in a square cross-section visualization channel within Liquid Helium Flow Visualization Facility (LHFVF). In the adiabatic flow case, visualization results confirm the existence of the turbulent boundary layer, with the measured velocity profiles being in reasonable agreement with empirical correlations for the classical fluids. No temperature dependence to the velocity profiles is observed within the temperature range tested (1.65 K to 2.10 K). We also tested the case of thermal counterflow in the horizontal channel without net flow. Heater powers ranging from 0.4 kW/m2 to 6.6 kW/m2 were applied to the channel at two different bath temperatures, 1.80 K and 1.95 K. We observe millimeter size vortices randomly located in the transient velocity field as measured by the tracer particles. The mean velocity results confirm that the tracer particles do not exactly track the normal fluid component motion, an effect which was observed by previous researchers with vertically oriented thermal counterflow channels. No turbulent boundary layer is observed in this case. A quantitative comparison with previous research in this area is also presented. Finally, we examine forced flow He II with constant applied heat flux, in which the forced flow is coupled with the thermal counterflow. In this case, the measured particle velocity fields show a similar flow pattern as the adiabatic case and the turbulent boundary layer remains. The mean velocity of the tracer particles is seen to be greater than the flow velocity and increases linearly with the normal fluid velocity; however, the rate of increase is less than predicted based on the two-fluid model. Observing and quantifying He II flow velocity fields can extend our knowledge of He II fundamentals and facilitate the refining of existing He II fluid dynamics models.
Show less - Date Issued
- 2007
- Identifier
- FSU_migr_etd-0417
- Format
- Thesis
- Title
- Stochastic Clustering Auctions for Cooperative Task Allocation.
- Creator
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Zhang, Kai, Collins, Emmanuel G., Barbu, Adrian, Dommelen, Leon van, Cartes, David, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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This dissertation considers the problem of optimal task allocation for heterogeneous teams, e.g., teams of heterogeneous robots or human-robot teams. It is well known that this problem is NP hard and hence computationally feasible approaches must develop an approximate solution. It will be shown that the global cost of the task allocations obtained with fast greedy algorithms can be improved upon by using a class of cooperative auction methods called Stochastic Clustering Auctions (SCAs)....
Show moreThis dissertation considers the problem of optimal task allocation for heterogeneous teams, e.g., teams of heterogeneous robots or human-robot teams. It is well known that this problem is NP hard and hence computationally feasible approaches must develop an approximate solution. It will be shown that the global cost of the task allocations obtained with fast greedy algorithms can be improved upon by using a class of cooperative auction methods called Stochastic Clustering Auctions (SCAs). SCAs use stochastic transfers or swaps between the task clusters assigned to each team member, allow both uphill and downhill cost movements, and rely on simulated annealing. The choice of a key annealing parameter and turning the uphill movements on and off enables the converged solution of a SCA to slide in the region between the global optimal performance and the performance associated with a random allocation. The first SCA developed in this research, called GSSCA, is based on a Gibbs sampler, constrains the stochastic cluster reallocations to simple single transfers or swaps, and is applicable to heterogeneous teams. For homogeneous teams this dissertation presents a new and more efficient SCA, called SWSCA, based on the generalized Swendsen-Wang method, which enables more complex and efficient movements between clusters by connecting tasks that appear to be synergistic and then stochastically reassigning these connected tasks. For heterogeneous teams this dissertation proposes a HYbrid Stochastic Clustering Auction, called HYSCA. In HYSCA the auctioneer makes stochastic movements with single tasks when the auctioneer negotiates with heterogeneous agents and makes stochastic movements with interconnected tasks when the auctioneer negotiates with homogeneous agents. For centralized auctioning extensive numerical experiments were used to compare GSSCA with greedy auctioning methods for homogeneous teams and heterogeneous teams in terms of costs and computational and communication requirements. A series of random simulations showed that SWSCA was able to obtain significantly greater cost improvements than GSSCA for both the greedy and non-greedy cases for homogeneous teams and HYSCA was able to obtain significantly greater cost improvements than GSSCA for heterogenous teams. For distributed auctioning simulation results are presented from random scenarios and for selected benchmark auction patterns with a focus on a comparison of the performance achieved with distributed and centralized GSSCA. Finally the distributed SWSCA and HYSCA is evaluated in numerical experiments in which the communication links between agents were motivated by a generic topology called a ``scale free network.'
Show less - Date Issued
- 2010
- Identifier
- FSU_migr_etd-0533
- Format
- Thesis
- Title
- Magnetic MEMS and Its Applications.
- Creator
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Zheng, Pan, Chen, Ching-Jen, Haik, Yousef, Zheng, Jim P., Chandra, Namas, Kalu, Peter, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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This research is to investigate the performance of mini and micro devices driven magnetically through simulations and experiments. Micro-Electro-Mechanical Systems (MEMS) invoking magnetic coupling were designed and tested. Scaled up models and numerical simulation of the micro spiral channel flow were also presented. Magnetic devices can generate larger forces for larger distance than their electrostatic counterparts; the energy density between the magnetic plates is usually larger than that...
Show moreThis research is to investigate the performance of mini and micro devices driven magnetically through simulations and experiments. Micro-Electro-Mechanical Systems (MEMS) invoking magnetic coupling were designed and tested. Scaled up models and numerical simulation of the micro spiral channel flow were also presented. Magnetic devices can generate larger forces for larger distance than their electrostatic counterparts; the energy density between the magnetic plates is usually larger than that between the electric plates. Properly designed, magnetic actuators can be made to hold high torques with no intervening wires. Magnetic actuation may be considered a feasible method to drive the MEMS with advantages. Pulsed laser deposition method is used for growing magnetic material to the surface of micro device. Magnetic material properties are investigated. A permanent magnet made of NdFeB is used as a target for pulsed laser deposition to produce the thin film on a micro device which may induce magnetic coupling with external magnet sources. The properties of the thin film formed at different substrate temperatures and effects of external magnetic field to the thin magnetic film are presented. A mini screw pump invoking the magnetic driven system is demonstrated and its working performance is verified experimentally. The experiment on mini screw pump is to demonstrate the advantages of magnetic coupling and to verify the feasibility of magnetic coupling concept in a real device. The mathematical modeling and numerical simulations for magnetic coupling are also carried out. Further, the design and microfabrication technologies are introduced for a magnetically driven micro gear and micro viscous pump. Through the study of several experiments, improvements for designs are made. Due to the challenge in testing the actual microdevices, scaled-up experiments for magnetically driven viscous pumps are made. These studies simulate the performance of the micro size counterpart. In addition, the analyses of flow in micro size channels are made. Boundary conditions required for a proper simulation are discussed. Numerical simulations required for a pump performance are given. The factors to affect the pump performance are discussed based on the theoretical model, experiment and numerical simulation results.
Show less - Date Issued
- 2004
- Identifier
- FSU_migr_etd-0524
- Format
- Thesis
- Title
- Quench Induced Degradation in Bi2Sr2Cacu2O8+X at 4.2 K.
- Creator
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Effio, Timothy, Schwartz, Justin, Hruda, Simone Peterson, Ordonez, Juan, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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Superconducting magnet systems are the enabling technology for several research fields, e.g., experimental high-energy physics and fusion. Advanced superconducting magnet systems are strongly needed to achieve ever-higher beam energy in particle accelerators. They are also extensively used in plasma confinement for fusion. The energy stored in a magnet converts to heat when the magnet is quenching, i.e., a state change from superconducting to normal. The temperature increase and the high turn...
Show moreSuperconducting magnet systems are the enabling technology for several research fields, e.g., experimental high-energy physics and fusion. Advanced superconducting magnet systems are strongly needed to achieve ever-higher beam energy in particle accelerators. They are also extensively used in plasma confinement for fusion. The energy stored in a magnet converts to heat when the magnet is quenching, i.e., a state change from superconducting to normal. The temperature increase and the high turn-to-turn voltage developed in a quench may degrade or damage the magnet. Thus, one of the key issues for the successful operation of superconducting magnets is the quench detection and protection. This thesis discusses the self-field quench behavior of Bi2Sr2CaCu2O8+x (Bi2212) short samples and coils with the purpose of discovering key critical quench conditions that cause loss in critical current (Ic) of the conductor. Bi2212 tapes and round wires are investigated in short sample quench experiments. The experiments are conducted by means of heater induced quenching, and V(t) and T(t) data during a quench is recorded. The minimum quench energy (MQE) and normal zone propagation velocity (NZPV) are determined for both conductors. Using the collected data, and measuring the Ic of samples after quenching, critical values for energy deposited into the conductor via Joule heating (E), maximum temporal temperature gradient (dT/dt|max), maximum spatial temperature gradient (dT/dx|max) and maximum temperature (Tmax) that cause loss in Ic are determined. These quench conditions are varied in order to determine specifically what the critical values for each are. It was determined that while the tape short samples exhibited higher stability than the round wires, their NZPV was excessively slower and critical quench conditions significantly smaller. Coil quench experiments where conducted on round wires due to their proven resilience to quench induced degradation during short sample experimentation. In similar fashion to short samples, MQE and NZPV were determined for coils, as operating conditions and conductor batch varied. Coil quench experiments where also conducted via means of "hot-spot" generation using a heater. It was concluded that the coils exhibited larger stability, yet slower NZPV than short sample round wires. The critical quench conditions that do not cause loss in Ic to the conductor agreed with those determined in the short sample round wire experiments. This allows for the conclusion that critical quench conditions are intrinsic to the conductor and not dependant on operating conditions. The dependence of quench behavior on sample Ic and current sharing temperature (Tcs) is also observed. It is noticed that with smaller Tcs, NZPV increases and stability decreases. Furthermore, inhomogeneous Ic and Tcs along the length of the conductor allow for inhomogeneous quench behavior. In turn quench conditions are difficult to predict, and vary between samples.
Show less - Date Issued
- 2008
- Identifier
- FSU_migr_etd-0597
- Format
- Thesis
- Title
- Reatime Dynamic Load Shedding for Shipboard Power Systems.
- Creator
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Ding, Zhiping, Cartes, David A., Collins, Emmanuel G., Luongo, Cesar, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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The electric power systems in U.S. Navy ships supply energy to sophisticated systems for weapons, communications, navigation and operation. The reliability and survivability of the shipboard power systems (SPS) are critical to the mission of a ship, especially under battle conditions. As part of the shipboard power system may become unavailable due to attack, emergency control actions such as load shedding should be taken for the ship to survive. A load shedding system disconnects selected...
Show moreThe electric power systems in U.S. Navy ships supply energy to sophisticated systems for weapons, communications, navigation and operation. The reliability and survivability of the shipboard power systems (SPS) are critical to the mission of a ship, especially under battle conditions. As part of the shipboard power system may become unavailable due to attack, emergency control actions such as load shedding should be taken for the ship to survive. A load shedding system disconnects selected loads from a power system to keep the remaining portion of the system operational. Current SPS load shedding is normally provided in several stages or levels, which only shed loads based on fixed priority categories [1]. Moreover, generally the loads are shed manually. This thesis presents a new realtime dynamic load shedding scheme for Navy SPS. In the proposed load shedding scheme, analytic hierarchy process (AHP) is adopted for dynamically prioritizing loads based on changing priorities of loads and system critical natures of loads. AHP is a multicriteria decision making methodology that produces a ranking among various alternatives. The load shedding scheme maximizes various system benefits and minimizes load curtailment. Expert system is used to facilitate the load shedding decision-making process. An illustration of the developed load shedding scheme (LSS) is presented. The proposed LSS is applied to a test SPS simulated in a Real Time Digital Simulator® (RTDS).
Show less - Date Issued
- 2006
- Identifier
- FSU_migr_etd-0735
- Format
- Thesis
- Title
- Thermal Analysis of a Solar Water Distillation and Electricity Generation System.
- Creator
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Anthony, Nikhil J., Ordonez, Juan Carlos, Alvi, Farrukh S., Oates, William S., Department of Mechanical Engineering, Florida State University
- Abstract/Description
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Solar stills are a popular choice for distilling water and removing harmful contaminants like arsenic and other minerals in some rural parts of Argentina. The processes involved in solar still are environment friendly as they are driven only by solar energy and do not require any external energy sources (such as electricity or energy from combustible products). The objective of the current study is to couple such a solar still with a photovoltaic array in order to generate both potable water...
Show moreSolar stills are a popular choice for distilling water and removing harmful contaminants like arsenic and other minerals in some rural parts of Argentina. The processes involved in solar still are environment friendly as they are driven only by solar energy and do not require any external energy sources (such as electricity or energy from combustible products). The objective of the current study is to couple such a solar still with a photovoltaic array in order to generate both potable water and electricity simultaneously. A model for such a system is developed and used to simulate the conditions of boath constant and variable irradiation. It is found that the water which evaporates in the solar still extracts the heat from the photovoltaic module consequently decreasing its temperature. The photovoltaic array coupled with the cogeneration system operates at temperatures which are lower than a stand-alone cell, thereby increasing the efficiency of the cell. With water and electricity as the byproducts of the system, the efficiency of the entire system is increased. Details pertaining to thermal analysis of the system are discussed.
Show less - Date Issued
- 2008
- Identifier
- FSU_migr_etd-0221
- Format
- Thesis
- Title
- Passive Variable Camber for Wheeled Mobile Robots.
- Creator
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Auchter, Joseph, Moore, Carl A., Krothapalli, Anjaneyulu, Clark, Jonathan, Hollis, Patrick, Roberts, Rodney, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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Wheeled vehicles typically suffer from kinematic wheel slip when moving over an uneven terrain. This wheel slip can lead to decreased localization ability, higher sensory and computational burdens, uncontrolled motion, and decreased power efficiency. In this work we explore a concept to improve the performance of wheeled mobile robots on outdoor terrain, called "Passive Variable Camber" (PVC). PVC adds an extra degree of freedom to each wheel, allowing it to tilt in a lateral direction. This...
Show moreWheeled vehicles typically suffer from kinematic wheel slip when moving over an uneven terrain. This wheel slip can lead to decreased localization ability, higher sensory and computational burdens, uncontrolled motion, and decreased power efficiency. In this work we explore a concept to improve the performance of wheeled mobile robots on outdoor terrain, called "Passive Variable Camber" (PVC). PVC adds an extra degree of freedom to each wheel, allowing it to tilt in a lateral direction. This motion is similar to the camber variations seen in automobiles and off-road vehicles. In this work we study the benefits of PVC for off-road mobile robots. First, we describe a novel kinematic simulation of a 3-wheeled mobile robot equipped with PVC and moving on uneven terrain. The purpose of our simulation is to verify that a WMR equipped with PVC can traverse rough ground without kinematic slip. In order to precisely model the way that three dimensional wheels roll over uneven ground, we adapt concepts developed for modeling dextrous robot manipulators. Our method provides a concise and manageable description of the kinematics and is easily adaptable to other vehicle designs of arbitrary complexity. The resulting equations tell us the instantaneous mobility (number of degrees of freedom) of the robot/ground system. We also show a way of specifying joint velocity inputs which are compatible with system constraints. Simulation results are presented for various types of terrain and scenarios which might be faced by autonomous vehicles operating in difficult environments. Our simulations show that the PVC-equipped robot can successfully negotiate extreme terrains without kinematic slip and with variations in camber angle in the range of -15 degrees to +15 degrees. A simulation which measured wheel slip for a standard robot without PVC indicates that the slip velocity for one wheel can be as high as 15 cm/sec for a wheel of radius 30 cm, and the resulting odometry error can be as high as 12.5% of the total distance traveled. Based on our simulation results, PVC has the potential to greatly improve the motion performance of wheeled mobile robots or any wheeled vehicle which moves outdoors on rough terrain by reducing wheel slip. We also present the design of an experimental setup to test PVC performance in the physical world. We designed a four-bar linkage which allows for the wheel camber to vary in response to the lateral forces at the wheel/ground contact. Instrumentation is described and a procedure is presented to determine the amount of wheel slip. This setup will allow us to verify that PVC reduces slip and improves motion performance.
Show less - Date Issued
- 2008
- Identifier
- FSU_migr_etd-0255
- Format
- Thesis
- Title
- Influence of Processing Mode on the Development of Nanostructure in Flux Melted Ag-40At%Cu Alloy.
- Creator
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Aujla, Dhanvir K., Kalu, Peter N., Hruda, Simone Peterson, Moore, Carl A, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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The influence of processing modes, swaging+drawing and rolling, on the development of nanostructures in flux melted Ag-40at%Cu alloy was studied using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, X-ray diffraction, nano hardness testing and micro hardness testing. Microstructural evolution in the materials can be classified into two strain regimes; low strains (ε component. The annealed texture was different from the as-deformed texture, and showed extensive...
Show moreThe influence of processing modes, swaging+drawing and rolling, on the development of nanostructures in flux melted Ag-40at%Cu alloy was studied using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, X-ray diffraction, nano hardness testing and micro hardness testing. Microstructural evolution in the materials can be classified into two strain regimes; low strains (ε component. The annealed texture was different from the as-deformed texture, and showed extensive perturbation of the components at high strains. The texture observed in the Ag phase of the rolled material showed that with the exception of the Shear2 {111} component, there was little or no effect of strain on the evolution of texture. The deformation texture components seen in Cu phase of the rolled material were near stable with the exception of the Shear3 {112} and Rotated Cube {013} components, which oscillated with strain. Texture components affected upon annealing in the Ag phase included the Shear2, Brass, S and Goss components. The Shear2 and Brass components had a mutually opposite relationship, with a decrease in one being accompanied with the increase in the other. The S component decreased uniformly at all strains, while the Goss component displayed an increase in intensity at ε=4.5 coinciding with the development of Ag precipitates. The volume fraction of the Rotated Cube component was high and of the same value at all strains in the Cu phase of the annealed rolled material suggesting that the material recrystallized during heat treatment, while the S component decreased at all strains similar to the Ag phase. The nano indentation data showed that cold working the material resulted in an increase in hardness by 66%. The swaged+drawn material and the annealed swaged+drawn material showed a hardness value that increased with increasing strain up to the peak value of ε=2.5 where it remained stable until ε=3.6 and dropped thereafter. The hardness of the rolled material seemed to decrease continuously with strain, while the hardness value of the annealed rolled material coincided with the values seen in the annealed swaged+drawn material at each strain. Micro hardness testing of the swaged+drawn material showed an oscillating behavior with increasing strain, while the micro hardness testing of the rolled material was similar in trend to the nano hardness data. Upon annealing, the micro hardness values of both processing methods were relatively the same for each strain, suggesting that the micro hardness values for the annealed material was independent of the processing mode.
Show less - Date Issued
- 2008
- Identifier
- FSU_migr_etd-0257
- Format
- Thesis
- Title
- Aerial Robot Navigation in Cluttered Urban Environments.
- Creator
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Shi, Dongqing, Collins, Emmanuel G., Palanki, Srinivas, Krothapalli, Anjaneyulu, Moore, Carl A., Department of Mechanical Engineering, Florida State University
- Abstract/Description
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Autonomous navigation systems for mobile robots have been successfully deployed for a wide range of planar ground-based tasks. However, very few counterparts of the previous planar navigation systems were developed for three-dimensional (3-D) motion, which is needed for unmanned aerial vehicles (UAVs). Safe maneuvering in complex environments is a major challenge for UAVs. Future urban reconnaissance and search missions will require UAVs to autonomously navigate through cluttered urban spaces...
Show moreAutonomous navigation systems for mobile robots have been successfully deployed for a wide range of planar ground-based tasks. However, very few counterparts of the previous planar navigation systems were developed for three-dimensional (3-D) motion, which is needed for unmanned aerial vehicles (UAVs). Safe maneuvering in complex environments is a major challenge for UAVs. Future urban reconnaissance and search missions will require UAVs to autonomously navigate through cluttered urban spaces. This research proposes two approaches for unmanned helicopter navigation in cluttered urban environments: a 3-D fuzzy behavioral approach and a 3-D vector field histogram (VFH) approach. Behavior-based control has been very successful for planar mobile robots navigation in unknown environments. A novel fuzzy behavioral scheme for navigating an unmanned helicopter in cluttered 3-D spaces is developed. The 3-D navigation problem is decomposed into several identical two-dimensional (2-D) navigation sub-problems, each of which is solved by using preference-based fuzzy behaviors. Due to the shortcomings of vector summation during the fusion of the 2-D sub-problems, instead of directly outputting steering sub-directions by their own defuzzification processes, the undefuzzified intermediate results of the sub-problems are fused to a 3-D solution region, representing degrees of preference for the robot movement. A new defuzzification algorithm that steers the robot by finding the centroid of a 3-D convex region of maximum volume in the 3-D solution region is developed. A fuzzy speed control system is also developed to ensure the efficiency and safety of the navigation. The VFH approach is very popular for planar mobile robots. A 3-D VFH approach to UAV navigation in cluttered urban environments is developed. A 3-D laser measurement system is used to obtain the obstacle distribution in this method. Instead of a 2-D Cartesian histogram grid as a world model, a 3-D spherical histogram mesh is applied. This 3-D histogram mesh is updated continuously with range data. The 3-D VFH method subsequently employs a two-stage data-reduction process in order to compute the desired control commands for the robot. In the first stage the 3-D histogram mesh is reduced to a 2-D polar histogram corresponding to all possible steering directions for the robot. In the second stage, a novel convex finding algorithm is applied to efficiently find candidate directions from the 2-D polar histogram. The most suitable sector within the candidates with the lowest value of a particular cost function is selected, and the steering of the robot is aligned with that direction. Substantial simulations have been carried out to demonstrate that the two algorithms proposed in this dissertation can smoothly and effectively guide an unmanned helicopter through unknown and cluttered urban environments. Comparison simulation results show that the 3-D VFH has the ability to travel shorter and smoother pathes at most of scenarios. However, the feature doesn't apply to the 2-D counterparts. The 2-D fuzzy behavioral method usually has a smoother path, but the 2-D VFH travels a shorter path in most of scenarios.
Show less - Date Issued
- 2006
- Identifier
- FSU_migr_etd-0317
- Format
- Thesis
- Title
- Influence of Initial Ecae Processing on Subsequent Development of Texture and Microstructure of Ofhc Copper.
- Creator
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Erb, Ana Marcia, Kalu, Peter N., Waryoba, Daudi, Moore, Carl, Oates, William, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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Oxygen free high conductivity (OFHC) copper was processed using equal channel angular extrusion (ECAE), drawing, swaging, or ECAE plus either drawing or swaging to a strain of 4. All processing was carried out at room temperature. The ECAE processing was carried out using route Bc with a die of 90° channel intersections. The influence of deformation path on the evolution of texture and microstructure in the as-deformed and annealed (at 250°C for 1 hour) conditions was documented using...
Show moreOxygen free high conductivity (OFHC) copper was processed using equal channel angular extrusion (ECAE), drawing, swaging, or ECAE plus either drawing or swaging to a strain of 4. All processing was carried out at room temperature. The ECAE processing was carried out using route Bc with a die of 90° channel intersections. The influence of deformation path on the evolution of texture and microstructure in the as-deformed and annealed (at 250°C for 1 hour) conditions was documented using orientation imaging microscopy (OIM), X-ray diffraction, and Vickers hardness testing. Processing by ECAE alone produced very fine and feathery microstructure (~ 1.2µm thickness) with weak - texture. Elongated grains parallel to the deformation direction were observed in wires processed by either drawing or swaging alone. Their texture was similar and can be described as +. Processing the wire by ECAE to a strain (ε) of ~3 followed by drawing or swaging to a cumulative strain of ~4 resulted in a + duplex texture. The texture in the ECAE plus swage wire was stronger than that of ECAE plus drawing. The Vickers hardness values for wires varied from 108 to 142 Hv, and difference in hardness was attributed to the variation in the substructure, which was minimal in the wires that underwent any form of swaging. Although the grain boundary character distribution (GBCD) of the wires in the as-processed condition was similar, the misorientation distribution function (MDF) was dependent on the processing method. While a high concentration of boundaries with 60 deg were found in the swaged wires, it was relatively absent in other wires, which had lots of 30-45 deg boundaries instead. Subsequent annealing of these wires at 250 deg C produced diverse results: recovered microstructure in any form of swaged wires, partially recrystallized in drawn or ECAE+drawn wires and fully recrystallized in materials processed by ECAE alone. The annealing behavior of these wires were correlated with the density of substructure and the ratio of the mobile (60 deg ) to immobile (30-45 deg ) boundaries. A ratio of mobile boundaries to immobile boundaries was greater than or equal to one resulted in a fully to partially recrystallized microstructure upon annealing, while a ratio less than 1 resulted in limited to no recrystallization upon annealing.
Show less - Date Issued
- 2009
- Identifier
- FSU_migr_etd-0556
- Format
- Thesis
- Title
- Feedback Control for Counterflow Thrust Vectoring with a Turbine Engine: Experiment Design and Robust Control Design and Implementation.
- Creator
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Dores, Delfim Zambujo Das, Jr., Emmanuel G. Collins, Alvi, Farrukh, Palanki, Srinivas, Krothapalli, Anjaneyulu, Lourenço, Luiz, Department of Mechanical Engineering, Florida...
Show moreDores, Delfim Zambujo Das, Jr., Emmanuel G. Collins, Alvi, Farrukh, Palanki, Srinivas, Krothapalli, Anjaneyulu, Lourenço, Luiz, Department of Mechanical Engineering, Florida State University
Show less - Abstract/Description
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Engineering research over the last few years has successfully demonstrated the potential of thrust vector control using counterflow at conditions up to Mach 2. Flow configurations that include the pitch vectoring of rectangular jets and multi-axis vector control in diamond and axisymmetric nozzle geometries have been studied. Although bistable (on-off) fluid-based control has been around for some time, the present counterflow thrust vector control is unique because proportional and continuous...
Show moreEngineering research over the last few years has successfully demonstrated the potential of thrust vector control using counterflow at conditions up to Mach 2. Flow configurations that include the pitch vectoring of rectangular jets and multi-axis vector control in diamond and axisymmetric nozzle geometries have been studied. Although bistable (on-off) fluid-based control has been around for some time, the present counterflow thrust vector control is unique because proportional and continuous jet response can be achieved in the absence of moving parts, while avoiding jet attachment, which renders most fluidic approaches unacceptable for aircraft and missile control applications. However, before this study, research had been limited to open-loop studies of counterflow thrust vectoring. For practical implementation it was vital that the counterflow scheme be used in conjunction with feedback control. Hence, the focus of this research was to develop and experimentally demonstrate a feedback control design methodology for counterflow thrust vectoring. This research focused on 2-D (pitch) thrust vectoring and addresses four key modeling issues. The first issue is to determine the measured variable to be commanded since the thrust vector angle is not measurable in real time. The second related issue is to determine the static mapping from the thrust vector angle to this measured variable. The third issue is to determine the dynamic relationship between the measured variable and the thrust vector angle. The fourth issue is to develop dynamic models with uncertainty characterizations. The final and main goal was the design and implementation of robust controllers that yield closed-loop systems with fast response times, and avoid overshoot in order to aid in the avoidance of attachment. These controllers should be simple and easy to implement in real applications. Hence, PID design has been chosen. Robust control design is accomplished by using §¤1 control theory in conjunction with the Popov-Tsypkin multiplier. The resulting optimization problem was solved using a real coded genetic-algorithm.
Show less - Date Issued
- 2005
- Identifier
- FSU_migr_etd-0695
- Format
- Thesis
- Title
- A Study of Thermal Counterflow in He II Using Particle Image Velocimetry (PIV) Technique.
- Creator
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Zhang, Tao, Sciver, Steven W. Van, Gibbs, Stephen J., Shih, Chiang, Cartes, David, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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This study is mainly focused on applying the Particle Image Velocimetry (PIV) technique to the unique fluid system of He II. Challenges associated with the application are identified and discussed in the context of the exceptional physical properties and experimental environment of He II. The particle dynamics in He II is studied, and two important parameters, slip velocity and relaxation time, are derived. Based on this information, the tracking characteristics of a variety of candidate...
Show moreThis study is mainly focused on applying the Particle Image Velocimetry (PIV) technique to the unique fluid system of He II. Challenges associated with the application are identified and discussed in the context of the exceptional physical properties and experimental environment of He II. The particle dynamics in He II is studied, and two important parameters, slip velocity and relaxation time, are derived. Based on this information, the tracking characteristics of a variety of candidate tracer particles, including commercially available solid particles and particles generated by freezing liquids and gases, are discussed, as well as their potential applications to liquid helium. It is indicated that polymer particles with a mean diameter of 1.7 μm and specific gravity of 1.1 are the most suitable for tracking the thermal counterflow in our experiments. To introduce these very fine particles into liquid helium, a simple seeding method based on the two-phase fluidized bed technology was developed. The seeding results show an adequate concentration and also a quite uniform spatial distribution of seeded particles. Using the PIV technique, velocity fields of He II thermal counterflow in steady state have been measured in a range of bath temperatures from 1.61 K to 2.0 K and applied heat fluxes from about 1.1 kW/m2 up to 13.7 kW/m2. A significant discrepancy between the measured particle velocity vp,a and theoretical normal fluid velocity vn,t is present at all the temperatures, and the ratio of vp,a/vn,t is most likely a temperature-independent constant around 0.5. Careful analysis suggests that this velocity discrepancy may be caused by an additional force from the superfluid component. A semi-empirical correlation for this force is developed. By adding the force to the particle dynamics equation, the analytical results are shown to be consistent with the experimental results. Also, the propagation of second sound shock and heat diffusion has been studied by measuring the instantaneous velocity fields of induced transient thermal counterflow. The arrival of shock front, effect of expansion fan, passage of shock tail, and the onset of heat diffusion are clearly observed from the particle velocity profiles versus time. The generated particle velocity profiles are compared and discussed in respect of the critical energy flux for the onset of quantum turbulence, and the additional force from the superfluid component is further addressed regarding its application to the transient state.
Show less - Date Issued
- 2004
- Identifier
- FSU_migr_etd-0546
- Format
- Thesis
- Title
- Effect of Interfaces on the Thermal, Mechanical and Chemical Characteristics of Carbon Nanotubes.
- Creator
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Shen, Guoan, Chandra, Namas, Andrei, Petru, Dommelen, Leon van, El-Azab, Anter, Shih, Chiang, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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The primary focus of this work is to explore the effect of interface on thermal, mechanical, and chemical properties of carbon nanotubes (CNTs) and the methods to modify the interface between CNTs and CNTs based composites. CNTs are potentially promising fibers for ultra-high-strength composites. The load transfer between the inner and outer tubes in multiwall nanotubes (MWNTs) has to be clearly understood to realize the potential of MWNTs in composites and other applications such as nano...
Show moreThe primary focus of this work is to explore the effect of interface on thermal, mechanical, and chemical properties of carbon nanotubes (CNTs) and the methods to modify the interface between CNTs and CNTs based composites. CNTs are potentially promising fibers for ultra-high-strength composites. The load transfer between the inner and outer tubes in multiwall nanotubes (MWNTs) has to be clearly understood to realize the potential of MWNTs in composites and other applications such as nano-springs, and nano-bearings. This dissertation studies the load transfer between the walls of MWNTs in both tension and compression using molecular dynamics simulations. It is found that only the minimal load is transferred to the inner nanotube in tension. The load transfer of capped nanotubes in compression is much higher than in tension. The presence of a few interstitial atoms between the walls of MWNTs can significantly improve the stiffness and enhance the load transfer to the inner nanotubes in both tension and compression. The modification of the interface of CNTs is a key factor for effectively using CNTs in many applications. The use of molecular statics and dynamics helps exploring ion irradiation as a method for functionalization of CNTs. It is found that ion bombardment of single and Multiwall carbon nanotubes creates vacancies and defects, which can act as high-energy sites for further chemical reactions; furthermore, ion irradiation of CNTs embedded in polymer matrix creates chemical attachments between CNTs and polymer matrix, enhancing the compositing process. Mechanical property simulations based on tension and pullout tests indicate that the chemical links between constituents in CNT–polymer systems result in higher load transfer, and hence, better composite properties. The effect of the interface turns out to be very crucial for printing in nanolithography processes. Molecular dynamics simulation is applied to extract interface properties, such as friction and adhesion, in nanoscale; later, the properties are input into a large-scale FEM model. As found, the protrusion problem is caused by many factors, such as strength of polymer at high temperature, thermal expansion properties, and depth of metal.
Show less - Date Issued
- 2006
- Identifier
- FSU_migr_etd-0310
- Format
- Thesis
- Title
- Development of a Solid Hydrogen Particle Generator for Feasibility Testing of a Solid Hydrogen Optical Mass Gauging System Prototype.
- Creator
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Adams, Thomas Edgar, Sciver, Steven W. Van, Luongo, Cesar A., Kalu, Peter N., Department of Mechanical Engineering, Florida State University
- Abstract/Description
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In recent years, NASA has become interested in densified fuels such as solid hydrogen. A change from liquid to solid-state fuel storage would result in an approximately 15% smaller onboard fuel tank, and thus a lower gross vehicle lift off weight. A lower lift off weight would allow for heavier payloads, more crewmembers, or longer space flight missions. The ability to store and use solid-state fuels would also lend to the possibility of more powerful atomic based propellants, such as boron...
Show moreIn recent years, NASA has become interested in densified fuels such as solid hydrogen. A change from liquid to solid-state fuel storage would result in an approximately 15% smaller onboard fuel tank, and thus a lower gross vehicle lift off weight. A lower lift off weight would allow for heavier payloads, more crewmembers, or longer space flight missions. The ability to store and use solid-state fuels would also lend to the possibility of more powerful atomic based propellants, such as boron or carbon, in the future. However, currently used techniques for liquid based mass gauging, required for quantifying the remaining mass in onboard fuel tanks, are not applicable to solid mass gauging. A new mass gauging technique is required to implement the use of solid-state fuel. It is required that this new mass gauging technique be capable of continuous measurement despite variations in fuel distribution, changes in gravitational forces, and other effects associated with mass in motion experienced during space flight. Furthermore, this technique and its related equipment must be minimally invasive to the fuel system, both mechanically and thermally. Advanced Technologies Group (ATG), has recently developed an optical mass gauging system with promising results in ground based tests on liquid hydrogen. The optical mass gauging system developed by ATG is coupled to a fuel tank via fiber-optic cables and utilizes the unique absorption spectra of molecular hydrogen, a tunable laser light source, a pseudo-integration optical sphere, and a spectrometer to gauge mass. A nearly monochromatic light, including an absorption wavelength for molecular hydrogen at a given intensity, is reflected uniformly within the pseudo integration sphere containing hydrogen. The intensity of the absorption wavelength is attenuated by hydrogen mass absorption, and the remainder is uniformly reflected about the internal surface of the pseudo-integration sphere. A ratiometric calculation is then used to approximate the attenuation due to mass, and ultimately the mass present, based on intensity measurements taken for an absorption wavelength and a non-absorption wavelength from the spheres internal surface. This system is minimally invasive and can be used to gauge quantities of solid mass by adjusting the emitted spectra to overlap the primary absorption wavelength of solid hydrogen at approximately 797.4 [nm]. In the present work, a solid hydrogen particle generator was designed and fabricated to test the response of the solid hydrogen optical mass gauging system (SHOMGS) prototype developed by ATG. The solid hydrogen particle generator consists of several components. Pre-cooled hydrogen gas (~80 K) was introduced from a cold trap into an encapsulated temperature controlled reservoir that was partially submerged in a bath of liquid helium at 4.2 K. This reservoir utilized the latent heat of the liquid helium bath as well as the heat capacity of the helium vapor to condense the hydrogen gas into liquid at approximately 19 K. Following condensation of a desired quantity of liquid hydrogen, the ullage in the reservoir was pressurized with helium gas to create a favorable pressure gradient for injection. A valve at the base of the reservoir was then opened to inject a fine spray of liquid hydrogen through an injection nozzle into a SHOMGS equipped pseudo-integration sphere containing a bath of liquid helium at approximately 4.2 K. The liquid helium bath of the sphere is used to solidify the droplets of liquid hydrogen into solid particles. A coaxial capacitor liquid level sensor was used in the liquid hydrogen reservoir to quantify the amount of mass injected from the particle generation system during each injection. Seven experiments were conducted. In each experiment, 10 to 20 mass injections were made to determine the response of the SHOMGS and the reproducibility of the results from the particle generation system. Raw data was recorded of the liquid hydrogen conditions before and after each injection, as well as associated changes in capacitance. These values were then used to calculate the injected mass. In addition, raw data was recorded from the SHOMGS regarding changes in reflected light intensity corresponding to each injection. Ratiometric analysis was performed on the light intensity data and this response was plotted against the quantities of mass injected to correlate the SHOMGS response. Following this battery of tests, several conclusions were determined. The solid hydrogen particle generator is capable of repeatable results and can provide known quantities of solid hydrogen with a calculated mass error of 10-20% dependant largely on the amount injected. The SHOMGS developed by ATG exhibits responses correlated to changes in mass injected. Following further development, this prototype could be modified for use on future space flight platforms.
Show less - Date Issued
- 2004
- Identifier
- FSU_migr_etd-0016
- Format
- Thesis
- Title
- A Microjet-Based Reactant Delivery Method for PEM Fuel Cells.
- Creator
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Deroche, Peter M., Krothapalli, Anjaneyulu, Greska, Brenton, Ordonez, Juan, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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A microjet-based reactant delivery method was implemented in a prototype PEM fuel cell. A commercially available fuel cell was procured that utilizes a conventional reactant delivery method. The prototype was designed with an identical active area so that number of variables leading to differences in performance between the two fuel cells would be minimal. The MEAs inside each fuel cell were identical. Both the prototype and commercially available cell were tested under a variety of operating...
Show moreA microjet-based reactant delivery method was implemented in a prototype PEM fuel cell. A commercially available fuel cell was procured that utilizes a conventional reactant delivery method. The prototype was designed with an identical active area so that number of variables leading to differences in performance between the two fuel cells would be minimal. The MEAs inside each fuel cell were identical. Both the prototype and commercially available cell were tested under a variety of operating conditions. Conditions that were tested include: low air stoichiometry flow rates, high air stoichiometry flow rates, varying relative humidity, varying hydrogen stagnation pressure, varying stack temperatures, and varying air backpressure. The performance of each fuel cell was compared for each set of test conditions. The results show that the prototype microjet fuel cell experienced lower activation losses than the commercially available fuel cell. Testing revealed several design flaws in the prototype. Also, there are indications that the microjet design allows the fuel cell to be less affected by high stack temperatures.
Show less - Date Issued
- 2008
- Identifier
- FSU_migr_etd-0071
- Format
- Thesis
- Title
- Experimantal and Theoretcal Study of Magnetic Hyperthermia.
- Creator
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Al-Hayek, Saleh Saad, Chen, Ching-Jen, Zheng, Jim P., Kalu, Peter N., Wu, Chifu, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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Localized magnetic particle hyperthermia heating treatment using ferromagnetic and superparamagnetic nanoparticles continue to be an active area of cancer research. Magnetic hyperthermia is a promising therapeutic method for treatment of cancer. It's based on the intratumoral deposition of biocompatible magnetic nanoparticles followed by exposure to a high-frequency electromagnetic field. The dissipation of energy connected especially with magnetic hysteresis losses, Neel and Brown...
Show moreLocalized magnetic particle hyperthermia heating treatment using ferromagnetic and superparamagnetic nanoparticles continue to be an active area of cancer research. Magnetic hyperthermia is a promising therapeutic method for treatment of cancer. It's based on the intratumoral deposition of biocompatible magnetic nanoparticles followed by exposure to a high-frequency electromagnetic field. The dissipation of energy connected especially with magnetic hysteresis losses, Neel and Brown relaxations results in a local heating of the active particles and consequently leads to the destruction of the cancer cells. Magnetic nanoparticle materials used has to have high specific power loss and a suitable temperature dependence of power loss allowed by an adjustment of the Curie temperature to about 315 K (43 °C). Overheating is ruled out due to a decrease of the magnetic hysteresis losses in the vicinity of the Curie temperature. One way to solve this task is the use of magnetic nanoparticles with the magnetic properties suitably modified by compositional variations. This dissertation, reports on localized magnetic hyperthermia studies using newly fabricated, as-synthesized, self-heating magnetic nanoparticles. Exposed to an alternating magnetic field, these nanoparticles act as localized heat sources at certain target regions inside the human body. Superparamagnetic nanoparticles provide attractive biotechnical and physiological advantages such as: direct injection through blood vessel due to ease of control of particle size, remote controlling of transport to tumor cells by externally applied magnetic field gradients, and resonant response to a time varying magnetic field resulting in heating up nanoparticles. In this dissertation, a report of the very promising and successful self-heating temperature rising characteristics of MnZn-ferrite, ZnGd-ferrite, GdZnCe-ferrite and ZnNd-ferrite nanoparticles obtained by chemical methods, mainly, co-precipitation process and under different applied magnetic fields and frequencies to confirm the effectiveness as hyperthermia agents. Magnetic and structural properties of these nanoparticles were analyzed in order to study the physical nature of self-heating characteristics and to investigate the effectiveness as hyperthermia agents in biomedicine. All four types of nanoparticle systems showed both superparamagnetic and ferromagnetic behaviors depending on particle sizes. Dominant magnetic heating mechanisms were studied and qualitatively identified, and a newly developed mathematical model to calculate the magnetic heating power was derived. The derived model proved to be in good agreement with the experimental results.
Show less - Date Issued
- 2007
- Identifier
- FSU_migr_etd-0150
- Format
- Thesis
- Title
- Design and Characterization of Mechanical Mesopumps.
- Creator
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Al-Riafai, Omar Moustafa, Haik, Yousef S., Chen, Ching-Jen, Wu, Chi Fu, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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This study focuses on characterizing meso scaled pumps. These pumps match in design to micro mechanical pumps produced using surface micromachining technology. The objective of this study is to characterize the performance of the meso scaled pumps experimentally, analytically, and numerically in order to gain a better understanding of the functional behavior of micropumps. Both types of actuations, magnetically and mechanically driven pumps, are considered in this thesis. In the magnetic...
Show moreThis study focuses on characterizing meso scaled pumps. These pumps match in design to micro mechanical pumps produced using surface micromachining technology. The objective of this study is to characterize the performance of the meso scaled pumps experimentally, analytically, and numerically in order to gain a better understanding of the functional behavior of micropumps. Both types of actuations, magnetically and mechanically driven pumps, are considered in this thesis. In the magnetic actuation, noninvasive coupling occurs between applied magnetic field and magnetically actuated material deposited on a movable actuator on the pump. Several advantages are reported when utilizing the magnetic actuation, including a reduction in the heat conduction from the motor to the bio fluids and a reduction on the hardware, particularly when using micro systems. A coupler was designed and manufactured to transmit the torque from the motor's shaft to the pump's shaft during mechanical coupling. The three micropumps to be characterized are the spiral pump, Von Karman pump, and crescent pump. These three micro pumps were fabricated at Sandia National Laboratory. In this study, three meso scaled pumps are characterized. The characterization for each mesopump was performed by pumping liquid water. A numerical simulation using CFDRC computer code was also performed for two viscous drag pumps (spiral, and Von Karman), and a comparison between the numerical, and experimental results was performed. Furthermore experimental data was compared to that predicted by analytical solution for spiral and crescent mesopumps. Characterization curves for each mesopump are then produced to provide a description of each pump's performance; moreover factors affecting the pump's performance are discussed.
Show less - Date Issued
- 2006
- Identifier
- FSU_migr_etd-0152
- Format
- Thesis
- Title
- Running over Unknown Rough Terrain with a One-Legged Planar Robot.
- Creator
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Andrews, Benjamin, Clark, Jonathan, Collins, Emmanuel, Oates, William, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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The ability to traverse over unknown, rough terrain is an advantage that legged locomotion has over wheeled systems. However, due to the complexity of multi-legged systems, researchers in legged robotics have not been able to reproduce the agility found in the animal kingdom. In an effort to reduce this complexity, researchers have developed single-legged models, or templates, to gain insight into the fundamental dynamics of legged running. Inspired by studies of animal locomotion,...
Show moreThe ability to traverse over unknown, rough terrain is an advantage that legged locomotion has over wheeled systems. However, due to the complexity of multi-legged systems, researchers in legged robotics have not been able to reproduce the agility found in the animal kingdom. In an effort to reduce this complexity, researchers have developed single-legged models, or templates, to gain insight into the fundamental dynamics of legged running. Inspired by studies of animal locomotion, researchers have proposed numerous control strategies to achieve stable one-legged running over unknown, rough terrain. One such control strategy incorporates energy variations into the system during the stance phase by changing the force-free leg length as a sinusoidal function of time. In this research, a one legged planar robot capable of implementing this and other state-of-the-art control strategies was designed and built. Both simulated and experimental results are used to determine and compare the stability of the proposed controllers as the robot is subjected to unknown drop and raised step perturbations equal to 25% of the nominal leg length. This study illustrates the relative advantages of utilizing a minimal-sensing, active energy removal control scheme to stabilize running over rough terrain.
Show less - Date Issued
- 2010
- Identifier
- FSU_migr_etd-0213
- Format
- Thesis
- Title
- Two-Phase Cryogenic Flowmeter: A Proof of Concept.
- Creator
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Ashmore, Robert H., Sciver, Steven Van, Luongo, Cesar, Collins, Emmanuel, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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A new concept for a two-phase flow-metering device has been developed and tested. The concept involves vapor-liquid two-phase flow through narrow, parallel channels which results in a laminar, stratified flow with a slope at the liquid-vapor interface. By measuring the height at various locations in the channel, the mass flow rate can be calculated. Two laminar two-phase flow meter systems were designed and tested. The first is a room temperature apparatus designed to confirm the basic...
Show moreA new concept for a two-phase flow-metering device has been developed and tested. The concept involves vapor-liquid two-phase flow through narrow, parallel channels which results in a laminar, stratified flow with a slope at the liquid-vapor interface. By measuring the height at various locations in the channel, the mass flow rate can be calculated. Two laminar two-phase flow meter systems were designed and tested. The first is a room temperature apparatus designed to confirm the basic concept. This apparatus, which uses air and water two-phase flow, consisted of 10 rectangular channels, each just over 1 mm wide, 74 mm high, and 305 mm long. To allow for observation of the flow behavior in the device, the channels in the room temperature device are made from borosilicate glass plates and are kept evenly spaced by a machined aluminum spacer plate. The apparatus was tested with water flow rates ranging from 0 to 0.126 liters per second and the air flow rates ranging from 0 to 4.72 standard liters per second. The results show a correlation between the flow quality and the slope of the water-air interface. Following the results from the room-temperature apparatus, a cryogenic two-phase laminar flow meter was designed and constructed. This apparatus, which uses saturated liquid nitrogen as the test fluid, consists of 30 narrow, parallel channels each measuring 2 mm wide, 102 mm tall, and 330 mm long. The liquid height is measured in the channel using capacitance-liquid level devices. The channel walls are made of G10 printed circuit boards (PCBs) with the capacitor conductors electroplated directly on the boards so that they produce minimal intrusion into the channel. The capacitors are wired in parallel to measure the sum of the capacitance across the 30 channels. A mutual capacitance effect was seen when trying to measure the flow-channel capacitors. This effect made it difficult to properly analyze the data. The differential pressure transducer also malfunctioned so that the pressure drop over the channel length could not be measured. This measurement is crucial in determining the fluid velocity in the experiment. Despite these problems, the device still showed the ability to clearly distinguish between liquid and vapor flows. There was also a correlation between the mass flow rate as the liquid level was changed. The room temperature apparatus and the cryogenic apparatus both showed that the laminar two-phase flow meter concept warrants further study. A strong correlation between the vapor and liquid mass flow rates has been seen and improvement of the current system would allow for proper measurement of the flow rates. Suggestions for future work to further the development of the device are given.
Show less - Date Issued
- 2006
- Identifier
- FSU_migr_etd-0245
- Format
- Thesis
- Title
- Active Control of High-Speed Free Jets Using High-Frequency Excitation.
- Creator
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Upadhyay, Puja, Alvi, Farrukh S., Hussaini, M. Yousuff, Kumar, Rajan, Clark, Jonathan E., Gustavsson, Jonas, Florida State University, College of Engineering, Department of...
Show moreUpadhyay, Puja, Alvi, Farrukh S., Hussaini, M. Yousuff, Kumar, Rajan, Clark, Jonathan E., Gustavsson, Jonas, Florida State University, College of Engineering, Department of Mechanical Engineering
Show less - Abstract/Description
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Control of aerodynamic noise generated by high-performance jet engines continues to remain a serious problem for the aviation community. Intense low frequency noise produced by large-scale coherent structures is known to dominate acoustic radiation in the aft angles. A tremendous amount of research effort has been dedicated towards the investigation of many passive and active flow control strategies to attenuate jet noise, while keeping performance penalties to a minimum. Unsteady excitation,...
Show moreControl of aerodynamic noise generated by high-performance jet engines continues to remain a serious problem for the aviation community. Intense low frequency noise produced by large-scale coherent structures is known to dominate acoustic radiation in the aft angles. A tremendous amount of research effort has been dedicated towards the investigation of many passive and active flow control strategies to attenuate jet noise, while keeping performance penalties to a minimum. Unsteady excitation, an active control technique, seeks to modify acoustic sources in the jet by leveraging the naturally-occurring flow instabilities in the shear layer. While excitation at a lower range of frequencies that scale with the dynamics of large-scale structures, has been attempted by a number of studies, effects at higher excitation frequencies remain severely unexplored. One of the major limitations stems from the lack of appropriate flow control devices that have sufficient dynamic response and/or control authority to be useful in turbulent flows, especially at higher speeds. To this end, the current study seeks to fulfill two main objectives. First, the design and characterization of two high-frequency fluidic actuators ($25$ and $60$ kHz) are undertaken, where the target frequencies are guided by the dynamics of high-speed free jets. Second, the influence of high-frequency forcing on the aeroacoustics of high-speed jets is explored in some detail by implementing the nominally 25 kHz actuator on a Mach 0.9 ($Re_D = 5\times10^5$) free jet flow field. Subsequently, these findings are directly compared to the results of steady microjet injection experiments performed in the same rig and to prior jet noise control studies, where available. Finally, limited acoustic measurements were also performed by implementing the nominally 25 kHz actuators on jets at higher Mach numbers, including shock containing jets, and elevated temperatures. Using lumped element modeling as an initial guide, the current work expands on the previous development of low-frequency (2-8 kHz) Resonance Enhanced Micro-actuators (REM) to design actuators that are capable of producing high amplitude pulses at much higher frequencies. Extensive benchtop characterization, using acoustic measurements as well as optical diagnostics using a high resolution micro-schlieren setup, is employed to characterize the flow properties and dynamic response of these actuators. The actuators produced high-amplitude output a range of frequencies, $20.3-27.8$ kHz and $54.8-78.2$ kHz, respectively. In addition to providing information on the actuator flow physics and performances at various operating conditions, the benchtop study serves to develop relatively easy-to-integrate, high-frequency actuators for active control of high-speed jets for noise reduction. Following actuator characterization studies, the nominally 25 kHz ($St_{DF} \approx 2.2$) actuators are implemented on a Mach 0.9 free jet flow field. Eight actuators are azimuthally distributed at the nozzle exit to excite the initial shear layer at frequencies that are approximately an order of magnitude higher compared to the \textit{jet preferred frequency}, $St_P \approx 0.2-0.3$. The influence of control on the mean and turbulent characteristics of the jet, especially the developing shear layer, is examined in great detail using planar and stereoscopic Particle Image Velocimetry (PIV). Examination of cross-stream velocity profiles revealed that actuation leads to strong, spatially coherent streamwise vortex pairs which in turn significantly modify the mean flow field, resulting in a prominently undulated shear layer. These vortices grow as they convect downstream, enhancing local entrainment and significantly thickening the initial shear layer. Azimuthal inhomogeneity introduced in the jet shear layer is also evident in the simultaneous redistribution and reduction of peak turbulent fluctuations in the cross-plane near the nozzle exit. Further downstream, control results in a global suppression of turbulence intensities for all axial locations, also evidenced by a longer potential core and overall reduced jet spreading. The resulting impact on the noise signature is estimated via far-field acoustic measurements. Noise reduction was observed at low to moderate frequencies for all observation angles. Direct comparison of these results with that of steady microjet injection revealed some notable differences in the initial development of streamwise vorticity and the redistribution of peak turbulence in the azimuthal direction. However, despite significant differences in the near nozzle aerodynamics, the downstream evolution of the jet appeared to approach near similar conditions with both high-frequency and steady microjet injection. Moreover, the impact on far-field noise was also comparable between the two injection methods as well as with others reported in the literature. Finally, for jets at higher Mach numbers and elevated temperatures, the effect of control was observed to vary with jet conditions. While the impact of the two control mechanisms were fairly comparable on non-shock containing jets, high-frequency forcing was observed to produce significantly larger reductions in screech and broadband shock-associated noise (BBSN) at select under-expanded jet conditions. The observed variations in control effects at different jet conditions call for further investigation.
Show less - Date Issued
- 2017
- Identifier
- FSU_FALL2017_Upadhyay_fsu_0071E_14154
- Format
- Thesis
- Title
- Ultrafast Laser Machining of Dielectrics: A Sharp Interface Model.
- Creator
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Woerner, Peter Christopher, Oates, William, Lin, Shangchao, Guo, Wei, Florida State University, College of Engineering, Department of Mechanical Engineering
- Abstract/Description
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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.
Show less - Date Issued
- 2016
- Identifier
- FSU_FALL2017_Woerner_fsu_0071N_13473
- Format
- Thesis
- Title
- Global Stability Analysis and Control of Compressible Flows over Rectangular Cavities.
- Creator
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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
Show less - Abstract/Description
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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.
Show less - Date Issued
- 2017
- Identifier
- FSU_FALL2017_Sun_fsu_0071E_14244
- Format
- Thesis
- Title
- Spatial Optimal Disturbances in Turbulent Boundary Layers.
- Creator
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Davis, Timothy B. (Timothy Brian), Alvi, Farrukh S., Sussman, Mark, Kumar, Rajan, Taira, Kunihiko, Oates, William, Uzun, Ali, Florida State University, FAMU-FSU College of...
Show moreDavis, Timothy B. (Timothy Brian), Alvi, Farrukh S., Sussman, Mark, Kumar, Rajan, Taira, Kunihiko, Oates, William, Uzun, Ali, Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering
Show less - Abstract/Description
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In this dissertation, disturbances leading to optimal energy growth in a spatially developing, zero-pressure-gradient turbulent boundary layer are examined. The slow development of the turbulent mean flow in the streamwise direction is modeled through a parabolized formulation to enable a spatial marching procedure. In the present framework, the linearized equations subject to a turbulent forcing are solved at particular wavenumber combinations. Conventional spatial optimal disturbance then...
Show moreIn this dissertation, disturbances leading to optimal energy growth in a spatially developing, zero-pressure-gradient turbulent boundary layer are examined. The slow development of the turbulent mean flow in the streamwise direction is modeled through a parabolized formulation to enable a spatial marching procedure. In the present framework, the linearized equations subject to a turbulent forcing are solved at particular wavenumber combinations. Conventional spatial optimal disturbance then arise naturally as the homogeneous solution whereas the particular solution captures the response to distributed forcing. A wave-like decomposition for the disturbance is considered to incorporate both conventional stationary modes as well as propagating modes formed by nonzero frequency/streamwise wavenumber and representative of convective structures naturally observed in wall turbulence. The optimal streamwise wavenumber, which varies with the spatial development of the turbulent mean flow, is computed locally via an auxiliary optimization constraint. The present approach can then be considered, in part, as an extension of the resolvent-based analyses for slowly developing flows. Optimization results reveal highly amplified disturbances for both stationary and propagating modes. In all cases, propagating modes surpass their stationary counterpart in both energy amplification and relative contribution to total fluctuation energy. We identify three classes of energetic modes associated with the inner, logarithmic and wake layers of the turbulent mean flow. The inner scaled modes are associated with the ubiquitous near wall streaks residing in the buffer layer. The outer scaled wake modes agree well with the large-scale motions that populate the wake layer. For high Reynolds numbers, however, the log modes increasingly dominate the energy spectra with the predicted streamwise and wall-normal scales in agreement with superstructures observed in turbulent boundary layers. Preliminary experimental measurements are performed to relate the energetic spanwise modes to the reported optimal disturbances.
Show less - Date Issued
- 2017
- Identifier
- FSU_FALL2017_Davis_fsu_0071E_14249
- Format
- Thesis
- Title
- Three Dimensional Control of High-Speed Cavity Flow Oscillations.
- Creator
-
Zhang, Yang, Cattafesta, Louis N., Tam, Christopher K. W., Taira, Kunihiko, Collins, E. (Emmanuel), Florida State University, College of Engineering, Department of Mechanical...
Show moreZhang, Yang, Cattafesta, Louis N., Tam, Christopher K. W., Taira, Kunihiko, Collins, E. (Emmanuel), Florida State University, College of Engineering, Department of Mechanical Engineering
Show less - Abstract/Description
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Cavity structures, like weapons bays and landing gear wells on aircraft, suffer from severe oscillations under high speed flow conditions. These oscillations are associated with intense surface pressure/velocity fluctuations inside the cavity which can radiate strong acoustic waves and cause structural damage. The physics of cavity flows have been studied for several decades with much of the effort put towards flow controls to reduce these oscillations. Geometric modifications of the cavity...
Show moreCavity structures, like weapons bays and landing gear wells on aircraft, suffer from severe oscillations under high speed flow conditions. These oscillations are associated with intense surface pressure/velocity fluctuations inside the cavity which can radiate strong acoustic waves and cause structural damage. The physics of cavity flows have been studied for several decades with much of the effort put towards flow controls to reduce these oscillations. Geometric modifications of the cavity structure are usually only effective for suppressing the oscillations within the designed flow conditions. Therefore, active flow control is more attractive for a wider application range. Previous research have proven that mass/momentum injection at the cavity leading edge can effectively suppress the pressure/velocity fluctuations. Due to the limited control authorities of current actuators, a steady actuation which introduces three-dimensional disturbances is studied to reduce the energy requirements of the actuator and improve the suppression of the oscillations over a wide range of free-stream Mach numbers. Surface fluctuating pressure measurements are acquired to determine the control performances of a number of 3-D actuation configurations. Flow fields, including velocity fields and density gradient fields, are measured to reveal the flow features with and without the flow control. Mathematical methods, including modal decomposition analysis, are further applied to study the dynamics of the flow field. All of these analyses together elucidate the effective 3-D actuation mechanism in the cavity flow control. The suppression of pressure fluctuations are obtained in both full-span and finite-span cavities. The successful flow control is found to be the redistribution of the energy in the shear layer by the counter-rotating-vortex pairs, which are introduced by the 3-D actuation in the cross-flow. In addition, a design guide for the actuator geometry is given based on the observations.
Show less - Date Issued
- 2017
- Identifier
- FSU_FALL2017_ZHANG_fsu_0071E_14127
- Format
- Thesis
- Title
- Dynamic Modeling and Motion Planning for Robotic Skid-Steered Vehicles.
- Creator
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Gupta, Nikhil, Collins, Emmanuel G., Edrington, Chris S., Clark, Jonathan, Oates, William S., Department of Mechanical Engineering, Florida State University
- Abstract/Description
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Skid-steered robots are commonly used in outdoor applications due to their mechanical simplicity, high maneuverability, and robustness. The maneuverability of these robots allows them to perform turning maneuvers ranging from point turns to straight line motion under ideal conditions (e.g., flat terrain and powerful actuators). However, sloped terrain, terrain with high friction, or actuator torque and power limitations can limit the achievable turning radii. The aim of this research is to...
Show moreSkid-steered robots are commonly used in outdoor applications due to their mechanical simplicity, high maneuverability, and robustness. The maneuverability of these robots allows them to perform turning maneuvers ranging from point turns to straight line motion under ideal conditions (e.g., flat terrain and powerful actuators). However, sloped terrain, terrain with high friction, or actuator torque and power limitations can limit the achievable turning radii. The aim of this research is to analyze and experimentally verify the dynamic and power models for skid-steered autonomous ground vehicles equipped with non-ideal (i.e., torque and power limited) actuators and moving on sloped terrains. In particular it investigates the ability of the proposed models to predict motor torques (including motor saturation), power requirement, and minimum turn radius as a function of terrain slope, vehicle heading, payload, terrain parameters and actuator characteristics. The experimental results show that the model is able to predict motor torques for the full range of turning radii on flat ground, i.e., from point turns to straight line motion. In addition, it is shown that the proposed model is able to predict motor torques (including motor saturation) and minimum turn radius as a function of terrain slope, vehicle heading, payload, terrain parameters and actuator characteristics. This makes the model usable for curvilinear motion planning tasks on sloped surfaces. The research uses these results along with Sampling Based Model Predictive Optimization to develop an effective methodology for generating dynamically feasible, energy efficient trajectories for skid-steered autonomous ground vehicles (AGVs) and compares the resultant trajectories with those based on the standard distance optimal trajectories. The simulated and experimental results consider an AGV moving at a constant forward velocity on both wood and asphalt surfaces under various loads. They show that a small increase in the distance of a trajectory over the distance optimal trajectory can result in a dramatic savings in the AGV's energy consumption. They also show that it is not difficult for distance optimal planning to produce trajectories that violate the motor torque constraints for skid-steered AGVs, which can result in poor navigation performance. In addition, the research motivates and provides a methodology that integrates the robot's dynamic model and actuator limitations, and the terrain models with SBMPO to exploit the vehicle momentum as a way to successfully traverse the difficult terrains such as steep hills, mud, or stiff vegetation patches. These scenarios are particularly critical for smaller robots with torque and power limited actuators, which as experimentally shown in this research can easily fail to accomplish their tasks in these environments. In particular, the experimental results showing the efficacy of the proposed methodology are presented for a vegetation patch and a steep hill. Finally, a discussion of the necessary perception work to fully automate the process is included. Further, for walking and running robots, analysis of the power consumption is particularly important for trajectory planning tasks as it enables motion plans that minimize energy consumption and do not violate power limitations of the robot actuators. The research here is motivated by the hypothesis that for certain regimes of operation (i.e., certain gait parameters), legged robots from the RHex family behave in a similar fashion to skid-steered robots while in general curvilinear motion. Hence, using the experience gained from skid-steered wheeled vehicles, presents models of the inner and outer side torques and power requirements for the XRL hexapedal robot. In addition, the applicability of the power model to energy efficient motion planning is illustrated for a walking gait on a vinyl surface.
Show less - Date Issued
- 2014
- Identifier
- FSU_migr_etd-8997
- Format
- Set of related objects
- Title
- Phase Equilibria of Fe-C Binary Alloys in a Magnetic Field.
- Creator
-
England, Roger Dale, Kalu, Peter N., Okoli, Okenwa, Shih, Chiang, Oates, William S., Ludtka, Gerard, Florida State University, College of Engineering, Department of Mechanical...
Show moreEngland, Roger Dale, Kalu, Peter N., Okoli, Okenwa, Shih, Chiang, Oates, William S., Ludtka, Gerard, Florida State University, College of Engineering, Department of Mechanical Engineering
Show less - Abstract/Description
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The deployment of high flux magnetic processing in industry requires the ability to model the expected results of a proposed processing, and the current assumptions in the literature did not reflect the actual outcome in measurements of ductile iron. Simple binary iron-carbon alloys of less than one weight percent carbon were thermo-magnetically processed and then compared with Gibbs free energy phase transformation predictions. The data was used to quantify the change in the Gibbs free...
Show moreThe deployment of high flux magnetic processing in industry requires the ability to model the expected results of a proposed processing, and the current assumptions in the literature did not reflect the actual outcome in measurements of ductile iron. Simple binary iron-carbon alloys of less than one weight percent carbon were thermo-magnetically processed and then compared with Gibbs free energy phase transformation predictions. The data was used to quantify the change in the Gibbs free energy associated with the addition of a static high flux magnetic field, which is complicated by the change in magnetic response as the iron carbon alloys pass through the Curie point. A current common practice is to modify Gibbs free energy by -12J per mole per Tesla applied, as has been reported in the literature. This current prediction practice was employed in initial experiments for this work and the experimental data did not agree with these predicted values. This work suggests two specific influences that affect the model, chemistry and magnetic dipole changes. First, that the influence of alloying elements in the original chemistry, as the samples in the literature were a manganese alloy with 0.45 weight percent carbon, as well as not being precisely controlled for tramp elements that commonly occur in recycled material, created a change that was not predicted and therefore the temperatures were incorrect. Also, the phase transformation in a high flux magnetic field was measured to have a different response under warming versus cooling than the normal hysteresis under ambient magnetism. The change in Gibbs free energy for the binary alloys was calculated as -3J per mole per Tesla in warming, and -8J per mole per tesla in cooling. The change from these values to the -12J per mole per Tesla previously reported is attributed to the change in chemistry. This work attributes the published increase in physical properties to the Hall-Petch relation as a result of the finer product phase nucleation created by the addition of a high flux magnetic field. Additionally, a pure iron sample was analyzed and found to be unique, in that the transformation temperature decreased with the application of a static magnetic field, opposite to what occurs in the iron carbon alloys. While the presence of a two-phase field is a viable cause due to the chromium impurity content in the sample creating a dilute binary alloy versus a pure element, this effect could also be attributed to the high magnetic field increasing the number of state variables present.
Show less - Date Issued
- 2014
- Identifier
- FSU_migr_etd-9170
- Format
- Set of related objects
- Title
- Three Dimensional Thermal Modeling of Friction Stir Processing.
- Creator
-
Vepakomma, K. Hemanth, Kalu, Peter, Chandra, Namas, Ordonez, Juan Carlos, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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It has been documented that heat is generated during friction stir processing. The amount of heat generated between the shoulder and the work piece during friction stir processing dictates the quality of the processed zone. Hence understanding the distribution of heat and obtaining the temperature contours will assist in understanding the general process of friction stir processing. In this thesis a three dimensional heat transfer model has been developed to obtain the temperature...
Show moreIt has been documented that heat is generated during friction stir processing. The amount of heat generated between the shoulder and the work piece during friction stir processing dictates the quality of the processed zone. Hence understanding the distribution of heat and obtaining the temperature contours will assist in understanding the general process of friction stir processing. In this thesis a three dimensional heat transfer model has been developed to obtain the temperature distribution in the work piece. An example problem was solved to understand the method of solving a transient heat transfer problem using ANSYS. The developed finite element model was validated by comparing the simulation results with experimental data from five different papers. A parametric study was carried out to understand the variation in temperature for different rotational and translational speeds. The variation of temperature with respect to thermal conductivity, specific heat and density was developed. A trend line equation which predicts the peak temperature attained during friction stir processing was also developed. The predicted peak temperature is used to obtain the temperature contours through out the work piece.
Show less - Date Issued
- 2006
- Identifier
- FSU_migr_etd-4565
- Format
- Set of related objects
- Title
- Characterization of Sapphire: for Its Material Properties at High Temperatures.
- Creator
-
Bal, Harman Singh, Oates, William S., Kumar, Rajan, Hellstrom, Eric, Florida State University, College of Engineering, Department of Mechanical Engineering
- Abstract/Description
-
There are numerous needs for sensing, one of which is in pressure sensing for high temperature application such as combustion related process and embedded in aircraft wings for reusable space vehicles. Currently, silicon based MEMS technology is used for pressure sensing. However, due to material properties the sensors have a limited range of approximately 600°C which is capable of being pushed towards 1000°C with active cooling. This can introduce reliability issues when you add more parts...
Show moreThere are numerous needs for sensing, one of which is in pressure sensing for high temperature application such as combustion related process and embedded in aircraft wings for reusable space vehicles. Currently, silicon based MEMS technology is used for pressure sensing. However, due to material properties the sensors have a limited range of approximately 600°C which is capable of being pushed towards 1000°C with active cooling. This can introduce reliability issues when you add more parts and high flow rates to remove large amounts of heat. To overcome this challenge, sapphire is investigated for optical based pressure transducers at temperatures approaching 1400°C. Due to its hardness and chemical inertness, traditional cutting and etching methods used in MEMS technology are not applicable. A method that is being investigated as a possible alternative is laser machining using a picosecond laser. In this research, we study the material property changes that occur from laser machining and quantify the changes with the experimental results obtained by testing sapphire at high-temperature with a standard 4-point bending set-up. Keywords: Sapphire, Bayesian analysis, thermomechanics, alumina
Show less - Date Issued
- 2015
- Identifier
- FSU_2015fall_Bal_fsu_0071N_12982
- Format
- Thesis
- Title
- Interfacial and Defect Structure in Nanoscale Ceria/Zirconia Superlattices.
- Creator
-
Dyer, Michael, El-Azab, Anter, Shih, Chiang, Kalu, Peter N., Chandra, Namas, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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Ceria and zirconia ceramics are well known for their ability to conduct oxygen ions, making them useful in constructing devices such as oxygen sensors and solid-oxide fuel cells. Increasing the ionic conductivity of these materials is a major point of interest, because this increases the efficiency and decreases the operating temperature of such fuel cells. Recent experimental results have shown that superlattices of alternating CeO2 and ZrO2 thin films that are alloyed with Gd2O3 exhibit...
Show moreCeria and zirconia ceramics are well known for their ability to conduct oxygen ions, making them useful in constructing devices such as oxygen sensors and solid-oxide fuel cells. Increasing the ionic conductivity of these materials is a major point of interest, because this increases the efficiency and decreases the operating temperature of such fuel cells. Recent experimental results have shown that superlattices of alternating CeO2 and ZrO2 thin films that are alloyed with Gd2O3 exhibit ionic conductivity that is superior to the individual monolithic materials. The enhanced ionic conductivity in these structures is attributed to the interfacial effects. Analytical modeling has shown that there are two possible mechanisms that lead to changes in the ionic conductivity: (a) an enhanced equilibrium concentration of oxygen vacancies in the layered structure arising as a part of the thermodynamic equilibrium across the interfaces, and (b) change in the defect formation energies and kinetic barriers due to interaction of defects with the epitaxial strain field in the heterogeneous system. The extent of this interaction is determined by the layer thickness and interfacial dislocation structure. Aiming to understand these mechanisms, a molecular dynamics (MD) study is performed to determine the interfacial and defect structures in pure and Gd-doped CeO2/ZrO2 superlattices, and the results are compared with the recent experimental observations.
Show less - Date Issued
- 2006
- Identifier
- FSU_migr_etd-0614
- Format
- Thesis
- Title
- Aeroacoustic Characteristics of Supersonic Twin Jets.
- Creator
-
Yerapotina, Sandeep, Anjaneyulu, Krothapalli, Alvi, Farukh, Engelen, Robert van, Department of Mechanical Engineering, Florida State University
- Abstract/Description
-
An experimental study was conducted to examine the aeroacoustic characteristics of supersonic twin jets and compare them to a single jet of equivalent area. Axisymmetric converging diverging nozzles having a fully expanded Mach number of 1.76 were operated at overexpanded and ideally expanded conditions. Planar velocity field measurements were made using Particle Image Velocimetry (PIV) at cold operating conditions. The results obtained show a decrease in potential core length for the twin...
Show moreAn experimental study was conducted to examine the aeroacoustic characteristics of supersonic twin jets and compare them to a single jet of equivalent area. Axisymmetric converging diverging nozzles having a fully expanded Mach number of 1.76 were operated at overexpanded and ideally expanded conditions. Planar velocity field measurements were made using Particle Image Velocimetry (PIV) at cold operating conditions. The results obtained show a decrease in potential core length for the twin jets. The twin jets were found to merge earlier when they were canted. Lower turbulence levels were observed for the twin jets compared to a single jet. The turbulence in the inter nozzle region of the canted twin jets was significantly reduced due to increased jet interaction. Far-field noise measurements for the twin jets were made at two azimuthal angles and compared to a single jet of equivalent diameter. Noise measurements showed a reduction in OASPL for the twin jets at most of the polar angles measured, with a 2 dB reduction in peak radiation direction. The OASPL levels of the twin jets showed a strong dependence on the azimuthal angle. Broadband shock noise was observed to have shifted to higher frequencies. Acoustic shielding was observed at some sideline angles, which caused significant reduction in high frequency noise.
Show less - Date Issued
- 2005
- Identifier
- FSU_migr_etd-0650
- Format
- Thesis
- Title
- Counterflow Heat Transfer in He II Contained in Porous Media.
- Creator
-
Dalban-Canassy, Matthieu, Sciver, Steven W. Van, Peterson, Janet, Luongo, Cesar, Ordonez, Juan, Englander, Ongi, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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This dissertation presents a study of steady He II (superfluid helium) counter flow heat transfer in porous media. Porous insulation were suggested as potential alternatives to conventional fully impregnated insulations in superconducting magnet technology. Superconducting magnets are usually cooled with He II. Use of porous insulation requires thus a good knowledge of the behavior of He II within porous materials, when set in motion or exposed to a heat source. The present work was focused...
Show moreThis dissertation presents a study of steady He II (superfluid helium) counter flow heat transfer in porous media. Porous insulation were suggested as potential alternatives to conventional fully impregnated insulations in superconducting magnet technology. Superconducting magnets are usually cooled with He II. Use of porous insulation requires thus a good knowledge of the behavior of He II within porous materials, when set in motion or exposed to a heat source. The present work was focused on the design of an apparatus capable of performing both steady and transient counterflow measurements in He II saturating a porous material with a geometry similar to potential candidate porous insulations. Those will most likely be composed of tapes of pre-impregnated woven ceramic fibers, forming a highly anisotropic compound, with a wide pore size distribution. The samples were provided by Composite Technology Development Inc. and are circular pellets (3.08 mm thick and 28.58 mm in diameter) of 20 compressed layers of pre-impregnated woven magnet insulation. The porous material was carefully characterized prior to experimental runs in He II. The samples exhibit a porosity and a permeability of respectively 20+-1% and 0.95x10^-14 m^2 for water measurements. The woven fiber rovings, composing the insulation, were found to be 0.04 mm^2 of average cross sectional area with fibers of average diameter of 10.6 micron. The He II experimental apparatus is composed of a vacuum insulated open channel whose top extremity is closed to a Minco heater. The temperature differences and pressure drops across the porous plug were measured by two Lakeshore barechip Cernox 1050BC thermometers and a Validyne DP10-20 differential pressure sensor. Applied heat fluxes ranged up to 0.5 kW/m^2 of sample cross section. Steady temperature differences, up to 570 mK, and pressure drops, up to 1800 Pa (limit of the sensor), measurements were performed at bath temperatures ranging from 1.6 to 2.1 K. In the low heat flux regime, the permeability data corroborate room temperature measurements. In the high heat flux regime however, we show evidence of the failure of previous models based on the inclusion of the tortuosity in the turbulent equation. We propose to include a constriction factor denoting an average maximum change in cross section in the heat path in addition to the increased path length denoted by the tortuosity. In the turbulent regime, this constriction factor is predominant as it enters in the model with a cubic power. Measurements of the critical characteristics, corresponding to the point of transition from the laminar regime, where Darcy law is applicable to the non-linear regime, where the heat flux adopts its characteristic cubic relationship, corresponding to the appearance of turbulence within He II are also reported. We obtained critical heat fluxes ranging from 20 to 70 W/m^2, Reynolds numbers of 0.5 to 4 and normal fluid velocities from 0.5 to 2.5 mm/s, varying with bath temperature. To confirm the room temperature measurements of permeability, we also conducted a forced flow experiment. Unfortunately, the flow range covered is outside of the laminar regime and does not permit an accurate estimation of the permeability. The results are however favorably comparable to earlier data recorded in the turbulent regime in similar flow conditions but with very different materials.
Show less - Date Issued
- 2010
- Identifier
- FSU_migr_etd-0855
- Format
- Thesis
- Title
- Effect of Magnetic Annealing on Texture and Microstructure Development in Silicon Steel.
- Creator
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Bacaltchuk, Cristiane Maria Basto, Garmestani, Hamid, Rollett, Anthony D., Zhang, Chuck, Gielisse, Peter, Shih, Chiang, Department of Mechanical Engineering, Florida State...
Show moreBacaltchuk, Cristiane Maria Basto, Garmestani, Hamid, Rollett, Anthony D., Zhang, Chuck, Gielisse, Peter, Shih, Chiang, Department of Mechanical Engineering, Florida State University
Show less - Abstract/Description
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The present work attempts to investigate the effect of magnetic annealing on texture and microstructure of grain non-oriented (GNO) cold rolled Fe-0.75%Si steel samples. The cold rolled specimens were annealed at constant magnitude of magnetic field, 17T, for different annealing times and at different magnitudes of magnetic field at a constant annealing time, 10 minutes. In order to evaluate the effect of the magnetic field, the cold rolled specimens were also annealed at the same conditions ...
Show moreThe present work attempts to investigate the effect of magnetic annealing on texture and microstructure of grain non-oriented (GNO) cold rolled Fe-0.75%Si steel samples. The cold rolled specimens were annealed at constant magnitude of magnetic field, 17T, for different annealing times and at different magnitudes of magnetic field at a constant annealing time, 10 minutes. In order to evaluate the effect of the magnetic field, the cold rolled specimens were also annealed at the same conditions (temperature, time and inert atmosphere) as for the magnetic annealing but without any magnetic field. EBSD/OIM, X-ray measurements and optical micrograph have being used to characterize the texture and microstructure of the samples after each annealing treatment. Magnetic annealing at high magnetic fields has shown to influence the final texture of the samples through changes in the ç, ã and á fibers. Magnetic field has not had a significant effect on the volume fraction of Goss-oriented grains but has affected the GBCD of these grains. High magnetic have shown to be a key factor for the improvement of texture and microstructure of Fe-0.75%Si steel.
Show less - Date Issued
- 2005
- Identifier
- FSU_migr_etd-0838
- Format
- Thesis
- Title
- Flooding Mitigation in a Microjet Based PEM Fuel Cell.
- Creator
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Badaru, Akintunde Adeoye, Krothapalli, Anjaneyulu, Greska, Brenton, Ordonez, Juan, Oates, William, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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An earlier work on reactant delivery in a Proton Exchange Membrane Fuel Cell using supersonic microjet impingement showed enhanced distribution of reactant and active cooling effect during operation. By comparative analysis with a commercial single cell unit, the microjet fuel cell offered significant cooling effect without sacrificing performance. Nonetheless, the microjet fuel cell was limited by its water management ability as it was susceptible to flooding and consequent degradation in...
Show moreAn earlier work on reactant delivery in a Proton Exchange Membrane Fuel Cell using supersonic microjet impingement showed enhanced distribution of reactant and active cooling effect during operation. By comparative analysis with a commercial single cell unit, the microjet fuel cell offered significant cooling effect without sacrificing performance. Nonetheless, the microjet fuel cell was limited by its water management ability as it was susceptible to flooding and consequent degradation in performance. By using a combination of independent microjets and serpentine flow channels, flooding of the fuel cell was significantly reduced. Electrode Impedance Spectroscopy, a non invasive and in-situ method, was utilized as a diagnostic tool to detect the onset of flooding as well as provide a qualitative assessment on the extent of flooding within the fuel cell. Polarization and Impedance spectroscopy measurements are used to characterize the performance of the fuel cell. To obtain useful power for most domestic applications, unit cells are stacked together. A prototype two-cell microjet based fuel cell has been designed and built. As the conventional bipolar configuration cannot be used in a microjet based fuel cell, connection between the cells is achieved externally. The characterization is done for different flow rates and relative humidity and temperature
Show less - Date Issued
- 2010
- Identifier
- FSU_migr_etd-0839
- Format
- Thesis
- Title
- Cooling, Thermal Design, and Stability of a Superconducting Motor.
- Creator
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Pienkos, Jules Edward, Luongo, Cesar A., Tixador, Pascal, Sciver, Steven W. Van, Baldwin, Thomas L., Masson, Philippe J., Department of Mechanical Engineering, Florida State...
Show morePienkos, Jules Edward, Luongo, Cesar A., Tixador, Pascal, Sciver, Steven W. Van, Baldwin, Thomas L., Masson, Philippe J., Department of Mechanical Engineering, Florida State University
Show less - Abstract/Description
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Great interest has been shown for the development of an All Electric Aircraft. There are many possible benefits and applications for the development of an All Electric Aircraft, such as monitoring severe weather or exploring the surface of other planets, and ultimately in civil aviation, a zero-emission aircraft. Design of the size and weight of the electrical systems for airplane use is important and a critical factor in this development is the propulsion of the aero-vehicle. One method to...
Show moreGreat interest has been shown for the development of an All Electric Aircraft. There are many possible benefits and applications for the development of an All Electric Aircraft, such as monitoring severe weather or exploring the surface of other planets, and ultimately in civil aviation, a zero-emission aircraft. Design of the size and weight of the electrical systems for airplane use is important and a critical factor in this development is the propulsion of the aero-vehicle. One method to increase power density of a motor is to use superconducting components. The development of a superconducting motor that provides enough power for an airplane is discussed. A Cessna-type aircraft is to be powered by a motor that utilizes high temperature superconducting (HTS) components in the inductor. This motor is a novel design that uses both BSCCO (bismuth strontium calcium copper oxide) tape wound in pancake shapes and single domain, bulk YBCO (yttrium barium copper oxide) plates to create powerful magnetic fields capable of meeting requirements for an aircraft. The HTS inductor design generates a magnetic field outward to a rotating, non-superconducting armature. The BSSCO pancakes generate a magnetic field to trap magnetic flux in the YBCO plates via the Field Cooling method (FC). The use of FC creates very powerful magnetic fields but requires a multi-step cooling schedule for the inductor design. To properly trap flux using FC, the BSCCO pancakes must first be cooled to the operating temperature and generate an applied magnetic field while the bulk YBCO plates remain above the critical temperature. The YBCO plates are then cooled near the operating temperature, thus trapping flux in the plates. The current in the pancakes is then reversed and the magnetic fields are generated, then the YBCO plates are further cooled to the steady state temperature. This process of cooling the BSCCO pancakes and then cooling the YBCO plates is called the 3-stage cooling. The cooling of the motor is by conduction due to the mobile application of aero-propulsion. The conduction-cooled inductor is constructed along with a cooling apparatus that includes an aluminum central cylinder attached to a cryocooler, G10 rings, and heaters that aid in the 3-stage cooling process. Simulations were performed that model the heat loads, cooling schedule from room temperature to operational temperature, and the 3-stage cooling to aid in the design. These modeling results show the temperature gradients in the inductor and HTS components and are verified experimentally. A full-scale, mockup inductor has been constructed and is cooled with a cryocooler in a cryostat. The cooling inductor final design is shown with modeling results and the proof-of-principle or a motor utilizing HTS materials in the inductor has been provided. A prototype of the motor should be built and tested based on these electromagnetic and cooling designs. The use of heaters near the YBCO plates is required in the 3-stage cooling design. The YBCO has trapped-flux that is dependent on the operating temperature and the stability of the trapped-flux is critical to the motor design. Work has been done that experimentally tests the stability of trapped flux in YBCO plates. A heat impulse is inputted into a YBCO sample that is fully penetrated in current via FC. The experiments were performed in a sample chamber that has temperature and applied magnetic field controllability. The change in the magnetic field and temperature of the sample is measured and analyzed before and after the heat pulse using Hall probes. The experimental data suggests that there is no thermal runaway loss in the trapped-magnetic flux for a small heat input and an operating temperature for which the sample has maximum stability. To explain the physics of the trends exhibited in the data, two models were developed. The first model uses an analytical approach to capture the overall trends exhibited by the data. The analytical model uses an energy balance based on the stored magnetic energy loss and change in thermal energy before and after the heat pulse is input into the sample. The second model is a finite element analysis approach using commercial software (Comsol) to gain a more in-depth analysis of the internal changes in the sample during the heat pulse. The Comsol model provides a tool to study the effect of the heat pulse on the current density and the effect of the cooling environment surrounding the sample. The models are able to capture the trends suggested by the experiment and provide insight into the fundamental phenomena that happen during the heat pulse. The sample studied in the experiment does indeed have a maximum stability point and it is explained by the modeling work. A cooling apparatus was designed to cool the inductor of a HTS motor. The electro-magnetic design utilizes field cooling to trap flux and this was accomplished with a 3-stage cooling process. The cooling design was validated using simulations and experimental data. The cooling apparatus showed the feasibility of the inductor to trap flux in the plates. The stability of the trapped flux was also studied. Experimental data shows that there is no thermal runaway when heat is inputted into a sample and an operating temperature exists that suggests a maximum stability. The physics of the stability experiment was uncovered using an analytical model and a FEA model. Also shown was the effect of the cooling environment on the sample during the heat impulse. The stability models showed that the data are the results of the cooling environment and the competing effects of current density and specific heat, both functions of temperature.
Show less - Date Issued
- 2009
- Identifier
- FSU_migr_etd-0821
- Format
- Thesis
- Title
- Low-Cost Concentrating Solar Collector for Steam Generation.
- Creator
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Dascomb, John, Krothapalli, Anjaneyulu, Greska, Brenton, Ord´o˜nez, Juan Carlos, Oates, William S., Department of Mechanical Engineering, Florida State University
- Abstract/Description
-
Concentrating solar power (CSP) is a unique renewable energy technology. CSP systems have the ability to provide electricity, refrigeration and water purification in one unit. This technology will be extremely helpful in improving the quality of life for many people around the world who lack the energy needed to live a healthy life. An economic parabolic dish concentrating system was built at the Sustainable Energy Science and Engineering Center (SESEC) at Florida State University in...
Show moreConcentrating solar power (CSP) is a unique renewable energy technology. CSP systems have the ability to provide electricity, refrigeration and water purification in one unit. This technology will be extremely helpful in improving the quality of life for many people around the world who lack the energy needed to live a healthy life. An economic parabolic dish concentrating system was built at the Sustainable Energy Science and Engineering Center (SESEC) at Florida State University in Tallahassee, Florida. The goal of the project was to provide 6.67 kW of thermal energy. This is the amount of energy required to produce 1 kW of electricity with a conventional micro steam turbine. The system had a price goal of $1000 per kW and must be simple enough to be maintained by non-technical personnel. A 14 m^2 fiberglass parabolic concentrator was made at SESEC to ensure simplicity of production and operation. The concentrator was coated with a highly reflective polymer film. The cavity type receiver was filled with sodium nitrate to act as a heat storage and transfer medium. The collection efficiency of the cavity was estimated at 70%. The gross thermal conversion efficiency of the system was 39%, which represented a 333% improvement over the first concentrator assembled at SESEC. At peak insolation 5.46 kW of thermal energy was produced. The material cost for the system was $3,052.
Show less - Date Issued
- 2009
- Identifier
- FSU_migr_etd-0833
- Format
- Thesis
- Title
- Surface Flow Measurements of Supersonic Impinging Microjets.
- Creator
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Davy, Charney Anchilyn, Alvi, Farrukh S., Shih, Chiang, Buzyna, George, Naughton, Jonathan, Department of Mechanical Engineering, Florida State University
- Abstract/Description
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Impinging supersonic microjets have been studied experimentally where both surface pressure and shear stress measurements and flow-field visualizations have been obtained. Microjets with diameters of 400 and 1000 microns have been investigated, operating at pressure ratios of 3, 5, and 8 and impinging plate distances of 2 to 8 diameters. The primary work concentrates on the application of oil-film interferometry to the flowfield in order to determine the surface shear stress. The results of...
Show moreImpinging supersonic microjets have been studied experimentally where both surface pressure and shear stress measurements and flow-field visualizations have been obtained. Microjets with diameters of 400 and 1000 microns have been investigated, operating at pressure ratios of 3, 5, and 8 and impinging plate distances of 2 to 8 diameters. The primary work concentrates on the application of oil-film interferometry to the flowfield in order to determine the surface shear stress. The results of this study indicate that high shear stress levels exist over a significant region around the impingement point and that the shear stress gradients are very high. For example, at a pressure ratio of 8, shear stress value at 2 and 11 nozzle diameters from the impingement point was found to be 300 Pa and 50 Pa, respectively. The shear stress distributions were compared with surface pressure distributions and to the limited computational results available for impinging jets. Although, a direct comparison is impossible due to lack of such data in literature, the trends observed in the present study appear to agree with those of larger supersonic impinging jets. The measurements indicate that oil-film interferometry provides repeatable, and reliable shear stress data in this complex flowfield - dominated by regions of high shear and large pressure gradients – which may not be amenable to other methods. The study also suggests some improvements, which can be implemented to further improve its reliability.
Show less - Date Issued
- 2003
- Identifier
- FSU_migr_etd-0799
- Format
- Thesis
- Title
- Visualization Study of Thermal Counterflow Turbulence in Superfluid 4He.
- Creator
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Gao, Jian, Guo, Wei (Professor of Mechanical Engineering), Li, Hui, Collins, Emmanuel G., Taira, Kunihiko, Pamidi, Sastry V., Florida State University, FAMU-FSU College of...
Show moreGao, Jian, Guo, Wei (Professor of Mechanical Engineering), Li, Hui, Collins, Emmanuel G., Taira, Kunihiko, Pamidi, Sastry V., Florida State University, FAMU-FSU College of Engineering, Department of Mechanical Engineering
Show less - Abstract/Description
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Superfluid 4He (He II) has been widely used as a coolant material in many engineering applications. Its unique heat transfer mode is the so-called thermal counterflow. The study of thermal counterflow will contribute to the design of He II based cooling devices and our understanding of quantum turbulence. However, due to the lack of effective visualization and velocimetry techniques, studying the fluid dynamics in superfluid 4He is very challenging. In this dissertation, we discussed the...
Show moreSuperfluid 4He (He II) has been widely used as a coolant material in many engineering applications. Its unique heat transfer mode is the so-called thermal counterflow. The study of thermal counterflow will contribute to the design of He II based cooling devices and our understanding of quantum turbulence. However, due to the lack of effective visualization and velocimetry techniques, studying the fluid dynamics in superfluid 4He is very challenging. In this dissertation, we discussed the development of a novel flow-visualization technique in He II based on the generation and imaging of thin lines of metastable tracer molecules. These molecular tracers are created via femtosecond-laser field-ionization of helium atoms and can be imaged using a laser-induced fluorescence technique. In steady state thermal counterflow measurement, we demonstrated that such tracer molecules are entrained by the normal fluid component. We revealed for the first time a laminar to turbulent transition in the normal fluid component. We found that the profile of the normal fluid in the laminar flow can exhibit quite different velocity profile compared to the laminar Poiseuille profile of classical fluid in a channel. In the turbulent flow state, the turbulence intensity is found to be much higher than that in classical channel flow. This turbulence intensity appears to depend primarily on temperature. We also found that the form of the second order transverse structure function deviates more strongly from that found in classical turbulence as the steady state heat flux increases, suggesting novel energy spectrum. In decaying counterflow turbulence, we studied the normal fluid flow via flow visualization and measured the quantized vortex line density using 2nd sound attenuation. Comparing the decay behavior of both fluids, we were able to produce a theoretical model to explain the puzzling decay behavior of the vortices. We were also able to determine the effective kinematic viscosity in a wide temperature range. Some preliminary results in the study of decaying grid turbulence were obtained, which allows us to examine the intermittent behavior of superfluid turbulence.
Show less - Date Issued
- 2017
- Identifier
- FSU_SUMMER2017_Gao_fsu_0071E_13828
- 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
Show less - Abstract/Description
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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.
Show less - Date Issued
- 2017
- Identifier
- FSU_SUMMER2017_Miles_fsu_0071E_14033
- Format
- Thesis
- Title
- Experimental Characterization of Photoresponsive Azobenzene Polymers.
- Creator
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Chowdhury, Sadiyah Sabah, Oates, William, Lin, Shangchao, Ordóñez, Juan Carlos, Florida State University, College of Engineering, Department of Mechanical Engineering
- Abstract/Description
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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.
Show less - 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
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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
Show less - Abstract/Description
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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.
Show less - 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
Show less - Abstract/Description
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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.
Show less - 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
Show less - Abstract/Description
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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.
Show less - 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
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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.
Show less - 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
Show less - Abstract/Description
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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.
Show less - Date Issued
- 2017
- Identifier
- FSU_SUMMER2017_Guha_fsu_0071E_14000
- Format
- Thesis
- Title
- Aeroacoustic Characteristics of Supersonic Impinging Jets.
- Creator
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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
Show less - Abstract/Description
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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.
Show less - 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
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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
Show less - Abstract/Description
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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.
Show less - Date Issued
- 2017
- Identifier
- FSU_SUMMER2017_Harmon_fsu_0071N_14049
- Format
- Thesis