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  • 1. Yasko, Isaiah Design and Fabrication of an Oil Conditioning System for a Hydrodynamic Thrust Bearing Testing Apparatus

    Master of Science (MS), Ohio University, 2022, Mechanical Engineering (Engineering and Technology)

    An oil conditioning system was designed and fabricated to be used in a research project for hydrodynamic thrust bearings. Once fabrication was completed, the system was integrated into a new hydrodynamic thrust bearing (HTB) testing system. The oil conditioning system was designed to function with specifications provided by the project sponsor Miba Bearings US, LLC. This thesis covers details of flow schematics, CAD models, Mechanical and thermal simulations, simulated heat load testing, and in-service HTB testing of the oil conditioning system.
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    Committee: Muhammad Ali (Advisor); Khairul Alam (Committee Member); Jason Trembly (Committee Member); Sergio Ulloa (Committee Member) Subjects: Mechanical Engineering; Systems Design

  • 2. Fais, Collier Design and Development of a Test Rig for Experimental Performance Evaluation of Fixed-Geometry Hydrodynamic Thrust Bearings: Comparison of Traditionally and Additively Manufactured Thrust Bearings

    Doctor of Philosophy (PhD), Ohio University, 2024, Mechanical and Systems Engineering (Engineering and Technology)

    This dissertation presents the design and development of a novel hydrodynamic thrust bearing test rig featuring a new (patent pending) pressure-feedback control system for maintaining static bearing alignment. This research aims to provide an enhanced understanding of how the critical operational characteristics of fixed-geometry hydrodynamic thrust bearings including minimum oil film thickness (MOFT), hydrodynamic pressure distribution, and bearing temperature are affected by variability in bearing pad taper geometry under different speed, load, and oil conditions. Further, a new (patent pending) additively manufactured (AM) thrust bearing fabricated using direct metal laser sintering (DMLS) is experimentally evaluated to determine in-service viability. To support the experimental data obtained in the variable taper experiment, a Matlab simulation code is developed using the Reynolds equation to generate numerically predicted performance data for direct comparison. The AM thrust bearing is experimentally compared to a traditionally manufactured cast alloy bearing with identical surface geometry. For the variable taper study, trends in performance established by the numerical analysis show mutually agreeable results compared to experimental data. The average percent deviation of the experimentally gathered change in MOFT as load is increased with respect to the numerically predicted values is 24%. Comparison of experimental to numerical pressure distribution data shows an overall average percent deviation of 32%. For the AM vs. traditionally manufactured bearing experiment, the AM bearing showed an average increase in minimum oil film thickness of 53%, an average increase in trailing edge hydrodynamic pressure of 116%, while exhibiting an average decrease in bearing temperature of 1%.
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    Committee: Muhammad Ali (Advisor); Khairul Alam (Committee Member); Arthur Smith (Committee Member); Zaki Kuruppalil (Committee Member); Jay Wilhelm (Committee Member) Subjects: Mechanical Engineering

  • 3. Lutfullaeva, Anbara Experimental Evaluation of Hydrodynamic Fixed Geometry Thrust Bearing Under Dynamic Load

    Doctor of Philosophy (PhD), Ohio University, 2024, Mechanical and Systems Engineering (Engineering and Technology)

    Hydrodynamic thrust bearings are extensively used in rotary machines. It is well known that different environmental conditions can strongly affect these machines and their rotating parts. Since the conditions can be static or dynamic, it is essential to identify the true operating conditions and its effect on the hydrodynamic thrust bearings for proper design. Oil film pressure, oil film thickness and temperature of oil are some of the most crucial operating parameters. Measuring the oil film pressure especially has been a very demanding task that many researchers have studied by mathematical means. In the present dissertation, tapered land hydrodynamic thrust bearing is experimentally investigated to understand its behavior under dynamic loading. To the best of the author's knowledge, published work on experimental testing of hydrodynamic fixed geometry thrust bearings under dynamic conditions for varying frequencies is non-existent. This dissertation is based on an experimental test rig that is designed, machined, and fabricated to apply and study dynamic loading conditions on hydrodynamic thrust bearings. The rig has the capability for measuring the oil film pressure, oil film thickness and the temperature of the oil. A HAAS-VF1 machine has been re-utilized as a housing for the dynamic test rig and a customized hydraulic loading system was used. Sinusoidal waves with varying frequencies (2-10 Hz), peak loads (150-350 lbs), and runner speed (1500 RPM and 2000 RPM) were applied to a thrust bearing of 0.002 in. taper depth. Each experimental test has been validated by pressure trends of leading, middle, and trailing edges of the pads of the bearing by comparing with static test rig results. In one of the presented cases, the 150 lbs peak load test at 1500 RPM showed a reduction of about 59.4%, 74.6%, and 57% in leading, middle, and trailing pressures, respectively, as the load frequency increased from 2 Hz to 10 Hz. Additionally, with the rise (open full item for complete abstract)
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    Committee: Muhammad Ali (Advisor) Subjects: Mechanical Engineering

  • 4. Alalawi, Huda THEORY AND APPLICATION OF FAR-FROM-EQUILIBRIUM HYDRODYNAMICS AND KINETIC THEORY

    PHD, Kent State University, 2023, College of Arts and Sciences / Department of Physics

    In the field of high-energy nuclear physics, ultrarelativistic heavy-ion collisions serve as a one-of-a-kind laboratory for investigating the extreme properties of matter. These collisions involve massive nuclei, such as lead or gold, colliding with energies in the trillions of electron volts per nucleon range. These collisions produce an environment where the strong force, as described by quantum chromodynamics (QCD), is the dominant force. In particular, the collisions generate a state of matter known as the quark-gluon plasma (QGP), which is characterized by a state of quarks and gluons that is not confined inside hadrons such as protons and neutrons. The QGP is an intriguing state of matter that provides insights into the behavior of dense astrophysical objects and the early universe. It is produced when the energy density of the collision reaches a critical threshold, resulting in the transition from the confined to the unconfined state of quarks and gluons. The QGP is a hot and dense system, with temperatures on the order of trillions of Kelvin and densities several orders of magnitude greater than the density of atomic nuclei in ordinary matter. In the initial phases of a heavy-ion collision, the system is far from thermal equilibrium and possesses a highly anisotropic pressure. The pressure anisotropy results from the longitudinal expansion being more rapid than the transverse expansion. The dynamics of the system cannot be adequately described by ideal hydrodynamics, which assumes local isotropic thermal equilibrium at all times. To account for the pressure anisotropy and non-equilibrium nature of the QGP, a framework known as anisotropic hydrodynamics has been developed. Anisotropic hydrodynamics (aHydro) is a useful tool for describing the evolution of the QGP, especially during the early non-equilibrium evolution of the QGP. It goes beyond the ideal hydrodynamic limit by incorporating dissipative transport coefficients, such as shear viscosity, which (open full item for complete abstract)
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    Committee: Michael Strickland (Advisor); Declan Keane (Committee Member); Mina Katramatou (Committee Member); Diana Goncalves Schmidt (Committee Member); Ruoming Jin (Committee Member) Subjects: Nuclear Physics; Particle Physics; Physics; Theoretical Physics

  • 5. Miller, Alexander Pore-Scale Sedimentary Structure, Pore-Size Distribution, and Flow Rate Control on the Emergence of the Hydrodynamic Dispersion Phenomenon

    MS, Kent State University, 2023, College of Arts and Sciences / Department of Earth Sciences

    Hydrodynamic dispersion emerges from the architecture of sedimentary rocks specific to depositional environments. Geologic heterogeneity, resulting from depositional processes, plays a critical role in describing the dispersion phenomena in sedimentary rocks. Questions remain in quantifying dispersion as a function of pore-scale heterogeneity and determining the spatial length scale needed for the solute transport phenomenon to transition from non-Fickian characteristics to Fickian characteristics. In this investigation, we digitally construct three pore-scale porous domain geometries to incorporate a) sedimentary architecture, i.e., graded, laminated, and random arrangement of grains, and b) a variety of pore-size distributions in each of the synthetic sedimentary architecture that accounts for variability resulting from sediment size distributions. We quantify geological heterogeneity in constructed sedimentary architectures by the standard deviation (σg) in the lognormal distribution of pore sizes. Flow and transport phenomenon is simulated using computational methods at different flow rates or Peclet number (Pe) regimes. Residence times and variance in flow field velocities are investigated as a function of σg. Hydrodynamic dispersion is quantified as a function of σg and shown to exhibit an exponential dependence. Flow rate effects on hydrodynamic dispersion display unique power-law exponents describing the impact of geologic heterogeneity. We observe a distinct spatial length scale needed for the transition from non-Fickian to Fickian transport. A magnitude of non-Fickian effects is quantified which highlights the importance of utilizing fully Fickian transport coefficients. Finally, the scaling behavior of dispersivity at the pore-scale is quantified, and the effects of flow rate and σg on dispersivity are described.
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    Committee: Kuldeep Singh (Advisor); Lichun Wang (Committee Member); Timothy Gallagher (Committee Member) Subjects: Fluid Dynamics; Geological; Geology

  • 6. Plencner, Eric Stress response of continued intensification of industrial production processes

    Doctor of Philosophy, The Ohio State University, 2022, Chemical Engineering

    This dissertation has three separate areas of focus. In the first, the Heat Shock Protein (HSP) expression of three different Chinese Hamster Ovary (CHO) cell lines is considered. Four different variables are considered to determine if there is an effect to the expression of HSP70 and HSP90. The experiments show a difference in the expression level of HSP between reactors where the air supply is through a ring sparger compared to those where the air supply is through a microsparger. These experiments show far higher variability between days in the microsparger reactor, and we find much greater differences between the highest and lowest point in the microsparger reactors than in the ring sparger reactors. When the reactors used both a ring sparger and a microsparger, eliminating the effect of the poorer Carbon Dioxide removal, we do not see any major difference when compared to the reactors with only a ring sparger. This suggests that the HSP expression difference seen in the microsparger reactor is not due to the stress caused by the smaller bubble, but rather it is due to the higher level of Carbon Dioxide seen in these reactors. When the use of an Alternating Tangential Flow (ATF) perfusion reactor was introduced in the reactor, allowing for the culturing of cells at far higher concentration than in a fed-batch reactor, the HSP expression is much lower than any fed-batch bioreactor, and is far more constant throughout the run than was seen in any fed-batch bioreactor. One set of experiments was performed with a larger scale reactor, 20L fed-batch and 200L perfusion. In these larger scale experiments, we see far lower HSP expression, and far less variability than was seen in the corresponding smaller scale reactor. In the final factor considered, there wasn't any observed difference between the expression level when the feed of a specific growth additive, Cell Boost 4, was varied between reactors. In the HEK cell line, the expression dramatically increas (open full item for complete abstract)
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    Committee: Jeffrey Chalmers (Advisor); David Wood (Committee Member); Eduardo Reategui (Committee Member); Andre Palmer (Committee Member) Subjects: Chemical Engineering

  • 7. Goss, Adam An Arbitrary Lagrange-Eulerian Investigation of HRAM Shallow Jet Pre-Spurt Formation and Time Sensitivities to Impact Plate Dynamics

    Doctor of Philosophy, The Ohio State University, 2021, Aerospace Engineering

    With dry bay fires persisting as a significant contributor to aircraft vulnerability despite chronicled developments in survivability technologies, an accurate fire prediction capability remains paramount for credible vulnerability assessments. Physics based modeling of the hydrodynamic ram (HRAM) fluid deposition process is a key component of such capability, wherein capturing the first instance of fluid spurt, referred to herein as shallow jet spurts, is a core focus. Such pre-spurts as they have been formerly identified have only been witnessed sporadically in HRAM spurt experiments. ALE3D, a first-principles multi-physics code was employed to model the shallow jet spurt phenomenon with spherical projectiles impacting water-filled tanks faced with aluminum panels, such that the underlying physics and sensitivities could be explored. Development and verification of the 2Daxisymmetric model is described relative to trends observed in a prior experimental campaign. Results from the verified model suggest shallow jet spurts have at least a quadratic sensitivity to the fundamental vibrational mode of the impact plate across impact velocities 610 – 1829 m/s (2000 – 6000 ft/s). It is further explained how shallow jet spurts are arrested for impacts at the two extremes of plate rigidity. This research constitutes the first fluid-structure modeling of shallow jet spurts which future three-dimensional analyses will expound upon.
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    Committee: Jeffrey Bons (Advisor) Subjects: Aerospace Engineering

  • 8. Khadka, Pravakar Three-Dimensional Hydrodynamic Modeling to Analyze Salinity Interaction of Coastal Marshland with a Lake: A Case Study of Mentor Marsh near Lake Erie, Ohio

    Master of Science in Engineering, Youngstown State University, 2020, Department of Civil/Environmental and Chemical Engineering

    Salinization is a global threat to the ecological functioning and development of the coastal wetlands. Therefore, the study of salinity interaction between the wetland and the coastal estuary is crucial to determine the salinity distribution and its variation in the coastal wetlands. This study, preeminently, was conducted to investigate the distribution of salinity in the Mentor Marsh wetland using a hydrodynamic model. The marsh is a coastal estuary system located within the Ohio Lake Basin, which has been experiencing increased levels of salinity from the early 1960s, especially after the placement of salt mine tailings near the marsh. Consequently, increased salinity has been inducing drastic vegetative change throughout the Mentor Marsh and leading to the rapid development of Phragmites australis. When dry, Phragmites australis is very prone to catch fire. Ten monitoring stations were established within the Mentor Marsh to monitor the salinity and record the hourly salinity, water level, and stream temperature data. The graphical analysis of the observed salinity was performed at several locations within the western basin of Mentor Marsh. Furthermore, a three-dimensional hydrodynamic Environmental Fluid Dynamics Code Plus (EFDC+) model was developed for the western section of the Mentor Marsh utilizing the measured data from five monitoring stations of the western basin. Most of the meteorological data needed for this model were obtained from the National Oceanic and Atmospheric Administration (NOAA). While cloud cover and precipitation data were acquired from nearby airports, solar radiation data were obtained from the United States Department of Agriculture (USDA). Similarly, bathymetry data were prepared by integrating the shoreline GIS shapefile of the Lake Erie and Mentor Marsh with a detailed survey conducted in the marina and adjoining marsh in order to appropriately represent the bathymetry in the EFDC+ model. The water levels at Lake Erie and Mentor (open full item for complete abstract)
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    Committee: Suresh Sharma PhD (Advisor); Shakir Husain PhD (Committee Member); Felicia Armstrong PhD (Committee Member); Thomas Mathis MS (Committee Member) Subjects: Civil Engineering; Environmental Engineering

  • 9. Hussain, Mallik Mohd Raihan Effective Nonlinear Susceptibilities of Metal-Insulator and Metal-Insulator-Metal Nanolayered Structures

    Doctor of Philosophy (Ph.D.), University of Dayton, 2020, Electro-Optics

    Nonlinear electromagnetic radiation (second and third harmonic) from the metal-insulator and metal-insulator-metal structures were measured and compared against predictions from the hydrodynamic models of plasmonics. This model incorporated higher-order terms stemming from electron tunneling and nonlocality. This study shows that, besides the linear optical parameter like permittivity, conductivity etc, changes in the nonlinear optical parameters, namely, second and third order susceptibilities (χ(2) and χ(3), respectively) can also be used to probe and compare the higher-order terms of the hydrodynamic model of plasmonics. Two insulator materials (ZnO and Al2O3) were used in two separate sets of experiments, and atomic layer deposition was used to cover the gold substrate with variable thicknesses of these insulator films (nanometer to sub-nanometer range). Large reduction in second and third harmonic signals was measured after the insulator film was deposited over the gold substrate revealing the spilled-out electronic states in the insulator region at the vicinity of the metal-insulator interface, which are dubbed metal insulator gap states. Then, the metal-insulator samples were spin-coated with Au-nanoparticle solution to prepare a metal-insulator-metal structures. For these structures, saturation and quenching of the third harmonic efficiencies were observed which were indicative of the capping of E-field enhancement due to the existence of higher order terms in the hydrodynamic model that accounts for nonlocality and quantum tunneling of electrons. A generalized 4 × 4 matrix method was utilized to calculate the effective χ(2) and χ(3) parameters that confirm the changes of effective material properties for ultra-thin films. These nonlinear coefficients, besides the linear permittivity ϵ and conductivity σ, can be a useful material parameter to study the effects of higher-order terms of hydrodynamic model.
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    Committee: Imad Agha Ph.D. (Committee Chair); Andrew Sarangan Ph.D. (Committee Member); Partha Banerjee Ph.D. (Committee Member); Michael Scalora Ph.D. (Committee Member) Subjects: Electromagnetics; Engineering; Optics

  • 10. Snyder, Troy On Hydrodynamic Lubrication using Perturbed Reynolds equation and CFD-FSI: Static and Dynamic Characteristics of Compliant Marine Bearings

    Doctor of Philosophy, University of Akron, 2019, Mechanical Engineering

    The compliant marine bearing is a type of journal bearing which features an elastomeric bushing and commonly utilizes water as the bearing lubricant. The term compliant follows from the deformation of the elastomeric bushing at substantially reduced hydrodynamic pressures compared to bearings with bushings comprised of metals such as bronze, brass, or steel. The operating regime of marine bearings under purely hydrdocynamic action is aptly called soft-EHL in which elasto-hydrodynamic lubrication occurs at sub-Hertizan pressures within the bearings' conformal contacts. Marine bearing bushings are typically profiled designs with lubricant grooves distributed around their circumference. The lubricant grooves serve as axial flow passages and contribute negligibly to the generation of hydrodynamic bearing pressures. The regions between the lubricant grooves are referred to as lands and generate hydrodynamic bearing forces which support static an dynamic radial loads applied to the bearings. Compliant marine bearings primarily serve in marine applications as stern tube and strut bearings, which support the propeller driveshaft at the rear of shipping vessels. This work provides a detailed theoretical development of a Reynolds equation-based model suitable to predict the static and dynamic performance of hydrodynamic bearings with compliant bushings. The dynamic performance is embodied in linearized dynamic coefficients which are calculated from a perturbed set of differential equations. The numerical solution of the model is exercised through a wide number of application cases to verify several modeling assumptions related to: bushing compliance, fluid inertia, and turbulence. Primarily, a simplified slider bearing geometry is investigated as it functions as a surrogate for a single stave in a full marine bearing. A FRF-based method to predict the dynamic behavior of hydrodynamic bearings (and seals) within a higher-fi (open full item for complete abstract)
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    Committee: Minel Braun (Advisor); S. Graham Kelly (Committee Member); Scott Sawyer (Committee Member); Atef Saleeb (Committee Member); Kevin Kreider (Committee Member) Subjects: Mechanical Engineering

  • 11. Swoger, Maxx Computational Investigation of Material and Dynamic Properties of Microtubules

    Master of Science, University of Akron, 2018, Physics

    Microtubules are an important component of the cytoskeleton of cells. They provide not only structural support, but also connectivity between different regions of the cell. The motor protein kinesin, for example, transports tethered cargo by walking along microtubules. Microtubules are macromolecules composed of two types of protein subunits, alpha and beta tubulin. Alternating alpha and beta units form long strands called protofilaments that are arranged with a helical pitch to form a hollow tube. This structure is responsible for the unusual mechanic and complex dynamic properties of microtubules in a liquid environment. In this work, we investigate material and dynamic properties of microtubules with computational methods. Since all-atom simulations are restricted to very short (~10 nm) sections of microtubules and very short (~10 ns) time scales, while dynamic processes span a much wider range of length and time scales, we focus on coarse-grained models: an interaction site model for Brownian dynamics simulations, a structural mechanics model for finite element calculations, and a continuum model to analyze normal modes. A comparison of mechanical properties of microtubules under an external force determined from finite element calculations and from Brownian dynamics simulations shows that the structural mechanics model describes a softer microtubule than the interaction site model. To investigate dynamic properties of microtubules in a finite-temperature liquid, we perform Brownian dynamics simulations with and without hydrodynamic interactions. After averaging out the fastest, thermal, motion, we are able to analyze transverse displacement results in terms of eigenmodes of an Euler-Bernoulli cantilever beam. Our results show that, in general, shorter microtubules have faster dynamics and that the inclusion of hydrodynamic interactions affects the slow modes of microtubules.
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    Committee: Jutta Luettmer-Strathmann PhD (Advisor); Yu-Kuang Hu PhD (Committee Chair); Robert R. Mallik PhD (Committee Member) Subjects: Biophysics; Condensed Matter Physics; Physics; Theoretical Physics

  • 12. Firouznia, Mohammadhossein The Hydrodynamic Interaction of Two Small Freely-moving Particles in a Couette Flow of a Yield Stress Fluid

    Master of Science (MS), Ohio University, 2017, Mechanical Engineering (Engineering and Technology)

    A great many industrial processes involve suspensions of noncolloidal particles in yield stress fluids. Investigating the microstructure is essential allowing the refinement of macroscopic equations for these complex suspensions. The interaction of two particles in a reversing shear flow of complex fluids is a guide to understand the behavior of complex suspensions. In this thesis, we study the hydrodynamic interaction of two small freely-moving spheres in a linear flow field of Newtonian, shear thinning and yield-stress fluids. This thesis includes the literature survey, the experimental procedure and the experimental results. In this study, we perform a series of experiments over a range of shear rates as well as different shear histories using an original apparatus and with the aid of conventional rheometry, Particle Image Velocimetry and Particle Tracking Velocimetry. We show that the Non-Newtonian nature of the suspending fluid strongly affects the shape of particle trajectories and the irreversibility. An important point is that non-Newtonian fluid effects can be varied and unusual. Depending on the shear rate, even a yield stress fluid might show hysteresis, shear banding and elasticity at the local scales that need to be taken into account. The flow field around one particle is studied in different fluids when subjected to shear. The results for one particle are used to describe the two particle interactions afterwards. In addition, we show that how a particle-particle contact and a non-Newtonian behavior result in relative trajectories with fore-aft asymmetries. We present well-resolved velocity and stress fields around the particles. Finally, we discuss that how the relative particle trajectories may affect the microstructure of complex suspensions and consequently the bulk rheology.
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    Committee: Sarah Hormozi PhD (Advisor); Peter Jung Professor (Committee Member); David Bayless Professor (Committee Member); Sumit Sharma PhD (Committee Member) Subjects: Chemical Engineering; Engineering; Mechanical Engineering; Physics

  • 13. Bhardwaj, Shubhendu Hybrid Numerical Models for Fast Design of Terahertz Plasmonic Devices

    Doctor of Philosophy, The Ohio State University, 2017, Electrical and Computer Engineering

    Electron-plasmonic devices are of strong interest for terahertz applications. In this work, we develop rigorous computational tools using finite difference time domain (FDTD) methods for accurate modeling of these devices. Existing full-wave-hydrodynamic models already combine Maxwell's and hydrodynamic electron-transport equation for multiphysical hybrid modeling. However, these multilevel methods are time-consuming as dense mesh is required for plasmonic modeling. Therefore, they are not suited for design and optimization. To address this issue, we propose new iterative ADI-FDTD-hydrodynamic hybrid coupled model. The new implementations provide time-efficient, yet accurate, modeling of these devices. It is demonstrated that for a typical simulation, up to 50% reduction in simulation-time is achieved with a nominal 3% error in calculations. Using the new tool-set, we investigate several devices that operate using the properties of 2D electron gas (2DEG). We provide one of the first multiphysical numerical analyses of these devices, giving accurate estimates of their terahertz performance. The developed tool allows simulation of arbitrary 2DEG based terahertz devices, providing useful and intuitive 2D field information. This has allowed understanding of the operation and radiation principles of these devices. Specifically, we examine the known plasma-wave instability in short-channel high electron mobility transistors (HEMTs) that leads to terahertz emissions at cryogenic temperatures. We also examine terahertz emitters that exploit resonant tunneling induced negative differential resistance (NDR) in HEMTs. Finally, using this tool we numerically demonstrate the existence of acoustic and optical-plasmonic modes within 2DEG bilayer systems in HEMTs. Methods for exciting and controlling these modes are also discussed enabling new physics among bilayer devices.
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    Committee: John Volakis (Advisor); Siddharth Rajan (Advisor); Kubilay Sertel (Committee Member); Teixeira Fernando (Committee Member); Niru Nahar (Committee Member); Karin Musier-Forsyth (Committee Member) Subjects: Electrical Engineering; Plasma Physics

  • 14. Ganga Dharan, Deepak Numerical Analysis of End-Sealed Squeeze-Film Damper Bearings using Moving Reference Frame Formulation

    MS, University of Cincinnati, 2016, Engineering and Applied Science: Mechanical Engineering

    Squeeze-film dampers (SFDs) are commonly used in aircraft engines because of their high damping coefficient and the associated ability to dissipate vibrations and improve the dynamic stability of rotor-bearing systems. The goal of the present work is to perform Computational Fluid Dynamics (CFD) simulation of uncavitated, end-sealed SFDs with axially centered or offset circumferential groove, and compare the simulation results for the tangential and radial forces with experimental data. For circular whirling motion of the SFD, a moving reference frame (MRF) formulation is used to transform the otherwise time-varying fluid domain to a time-independent domain, and enable an efficient steady-state simulation. The approach is first verified by comparing the simulation results with the Reynolds analytical solutions for long SFD (wherein pressure is a function of only the azimuthal direction, &theta) and short SFD (wherein pressure is a function of both &theta and the axial direction, z) bearings. The Reynolds solutions neglect inertia (Reynolds number Re = 0), whereas the computational model requires a non-zero Re, howsoever small. With Re = 0.96, the computed tangential force (directly proportional to damping) yields just 0.09% and 0.66% difference for the long and short SFD Reynolds solutions, respectively, thereby verifying the correct implementation of the MRF formulation. Next, the mathematical model used is validated by comparing the CFD results with available experimental data. The computed tangential force for the centered- and offset-groove configurations compares within 6.55% and 6.72%, respectively, with the data, suggesting that the simulation methodology developed can be used, within this tolerance, to predict the forces for end-sealed SFDs. Finally, a parametric study is conducted by varying geometrical parameters (radial clearance and groove position) and operating parameters (feeding pressure, feeding temperature, and whirling speed) for this flow. Groov (open full item for complete abstract)
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    Committee: Urmila Ghia Ph.D. (Committee Chair); Kirti Ghia Ph.D. (Committee Member); Jay Kim Ph.D. (Committee Member) Subjects: Mechanical Engineering

  • 15. Feister, Scott Efficient Acceleration of Electrons by an Intense Laser and its Reflection

    Doctor of Philosophy, The Ohio State University, 2016, Physics

    Here I present an experimental, theoretical, and computational exploration of an extremely efficient scheme for laser-based acceleration of electrons. A series of experiments were performed at the Air Force Research Laboratory in Dayton, OH, to show that a high-repetition-rate short-pulse laser (3 mJ, 40 fs, 1 kHz) normally incident on a continuous water stream can accelerate electrons in the back-reflection spray with >1% laser-to-electron efficiency for electrons >120 keV, and with >MeV electron energies present in large number. Characterization of the accelerated electrons was followed by explorations of appropriate focal conditions, pre-plasma conditions, and laser-intensity parameters. These experiments show clear signatures of plasma instabilities, with substantial 3ω/2 and ω/2 optical harmonics detected concurrently with efficient electron acceleration. Particle-in-cell (PIC) simulations of high-intensity laser interactions are able to reproduce the electron energies and acceleration efficiencies, as well as plasma instabilities. Analysis of the simulations suggest that electrons are accelerated by a standing wave established between incident and reflected light, coupled with direct laser acceleration by reflected light. Using hydrodynamic simulations of the laser pre-pulse interaction as initial conditions for PIC simulations of the main-pulse interaction clarifies mechanisms by which experimental manipulation of pre-pulse has effectively determined electron-acceleration efficiency in the laboratory.
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    Committee: Richard R. Freeman (Advisor); Linn D. Van Woerkom (Committee Member); Junko Shigemitsu (Committee Member); Michael Lisa (Committee Member) Subjects: Physics

  • 16. Mukherjee, Prithiviraj Generation of Drug-loaded Echogenic Liposomes using Microfluidic Hydrodynamic Flow Focusing

    MS, University of Cincinnati, 2016, Engineering and Applied Science: Electrical Engineering

    This work describes development of a microfluidic system for the synthesis of echogenic liposomes (ELIP) loaded with the thrombolytic drug rt-PA (recombinant tissue plasminogen activator). ELIP are phospholipid vesicles with encapsulated microbubbles. Drugs, genes, or bioactive gases encapsulated in ELIP can be delivered to specific tissue targets using ultrasound activation. Microfluidic devices were fabricated in Polydimethylsiloxane (PDMS), using the standard soft lithography methods and were optimized for flow rates and gas pressures to generate echogenic liposomes in the right size range and with good repeatability. The liposomes were generated in the size range of 2-20 µm, using octafluoropropane (OFP) and octfluorocyclobutane (C4F8) gases as core. Fluorescence microscopy was used to visualize encapsulation of the water soluble rt-PA drug. In future work, these liposomes could be used in non-invasive ultrasound-mediated drug delivery, to affect thrombolysis.
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    Committee: Ian Papautsky Ph.D. (Committee Chair); Madhuvanthi A. Kandadai Ph.D. (Committee Member); Chong Ahn Ph.D. (Committee Member); Christy Holland Ph.D. (Committee Member) Subjects: Engineering

  • 17. Miranda, Gregorio The Detection of Journal Bearing Cavitation with Use of Ultrasound Technology

    Master of Sciences (Engineering), Case Western Reserve University, 2016, EMC - Mechanical Engineering

    A method utilizing the implementation of ultrasound technology is developed to detect cavitation in an operating journal bearing. A modified Reynolds equation is derived and applied to a journal bearing design in order to determine the pressure distribution of the fluid film present in the bearing during operation. This model is used to predict the location of the low pressure region, or gaseous cavitation region, of the bearing to determine the target location for the ultrasound technology instrumentation. A journal bearing test bench apparatus was constructed under the guidance of the pressure distribution model. Ultrasound technology in the form of a small 7mm diameter 10MHz sensor is applied to the back side of the fabricated bearing, opposite of the predicted low fluid film pressure region of bearing operation. An experiment is conducted in order to compare the ultrasound signal attenuation when the measurement region is exposed to both high and low fluid film pressures. The results of the experimental testing indicate a correlation of the ultrasound signal response with whether the measurement region is exposed to high or low fluid film pressures from journal operation. Correlation of changes in signal attenuation with cavitation located in the low fluid film pressure region present itself as an increase in signal attenuation variability when compared to the signal measured in high fluid film pressure regions. The presence of gaseous cavities in the low fluid film pressure region is confirmed with the fabrication and operation of a translucent bearing of identical geometries. Cavities in the fluid film are observed in the low pressure region during operation of the translucent bearing, validating the presence of cavitation in the target region, further confirming the ability of the technique to detect cavitation in journal bearing operation.
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    Committee: Joseph Prahl (Committee Chair); Paul Barnhart (Committee Member); Roger Quinn (Committee Member) Subjects: Fluid Dynamics; Mechanical Engineering

  • 18. Zhang, Li FDTD Algorithm for Plasmonic Nanoparticles with Spatial Dispersion

    Master of Science, The Ohio State University, 2016, Electrical and Computer Engineering

    We develop a finite-difference time-domain (FDTD) algorithm incorporating the hydrodynamic Drude model for the permittivity of noble metals. This model incorporates spatial dispersion (nonlocal) effects on the permittivity. The resulting FDTD algorithm fully includes eddy current effects and is employed to study the extinction cross section of different metallic nanoparticles: nanospheres, nanoshells, nanospheroids, nanodisks, and nanorings, in the visible spectrum. It is observed that spatial dispersion can have significant effects on the extinction cross section of nanoparticles with characteristic sizes around 20 nm or below. For larger particles, the effect is mostly negligible. It is determined that inclusion of spatial dispersion yields two general trends on the behavior of the extinction cross section versus frequency as the particle size is reduced. The first is a blue-shift on the extinction spectrum and the second is an overall decrease on the extinction cross section as well as on the sharpness of resonance peaks. Also we find the strength of spatial dispersion effects do not have significant dependence on the orientation of nanoparticles.
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    Committee: Teixeira Fernando (Advisor); Anderson Betty (Committee Member) Subjects: Electrical Engineering; Electromagnetics; Electromagnetism; Physics

  • 19. Diaz Aldana, Luis Mathematical Modeling of Ammonia Electro-Oxidation on Polycrystalline Pt Deposited Electrodes

    Doctor of Philosophy (PhD), Ohio University, 2014, Chemical Engineering (Engineering and Technology)

    The ammonia electrolysis process has been proposed as a feasible way for electrochemical generation of fuel grade hydrogen (H2). Ammonia is identified as one of the most suitable energy carriers due to its high hydrogen density, and its safe and efficient distribution chain. Moreover, the fact that this process can be applied even at low ammonia concentration feedstock opens its application to wastewater treatment along with H2 co-generation. In the ammonia electrolysis process, ammonia is electro-oxidized in the anode side to produce N2 while H2 is evolved from water reduction in the cathode. A thermodynamic energy requirement of just five percent of the energy used in hydrogen production from water electrolysis is expected from ammonia electrolysis. However, the absence of a complete understanding of the reaction mechanism and kinetics involved in the ammonia electro-oxidation has not yet allowed the full commercialization of this process. For that reason, a kinetic model that can be trusted in the design and scale up of the ammonia electrolyzer needs to be developed. This research focused on the elucidation of the reaction mechanism and kinetic parameters for the ammonia electro-oxidation. The definition of the most relevant elementary reactions steps was obtained through the parallel analysis of experimental data and the development of a mathematical model of the ammonia electro-oxidation in a well defined hydrodynamic system, such as the rotating disk electrode (RDE). Ammonia electro-oxidation to N2 as final product was concluded to be a slow surface confined process where parallel reactions leading to the deactivation of the catalyst are present. Through the development of this work it was possible to define a reaction mechanism and values for the kinetic parameters for ammonia electro-oxidation that allow an accurate representation of the experimental observations on a RDE system. Additionally, the validity of the reaction mechanism and kinetic paramet (open full item for complete abstract)
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    Committee: Gerardine Botte Ph.D. (Advisor); Valerie Young Ph.D. (Committee Member); Gang Chen Ph.D. (Committee Member); Savas Kaya Ph.D. (Committee Member); Howard Dewald Ph.D. (Committee Member) Subjects: Chemical Engineering; Chemistry; Energy; Engineering

  • 20. Qiu, Zhi Event-by-event Hydrodynamic Simulations for Relativistic Heavy-ion Collisions

    Doctor of Philosophy, The Ohio State University, 2013, Physics

    In this thesis, I show my Ph.D. work on event-by-event hydrodynamic simulations for relativistic heavy-ion collision. I show that event-by-event hydrodynamic simulations have become an indispensable tool for studying relativistic heavy-ion collisions and how it can be used to explain many phenomena. In Chap. 2, I compare the previously dominating single-shot hydrodynamics with event-by-event hydrodynamic simulations which are now becoming mainstream. The event-by-event simulations are more realistic, but they are also very time consuming; the single-shot simulations are economical, but then the question arises as to whether they can be used as a sufficiently precise replacement for event-by-event simulations. I will compare these two simulation types for two popular initial condition models. I show that for the event averages of the multiplicity and elliptic and triangular flows, the time consuming event-by-event hydrodynamic simulations can, to a good approximation, be replaced by single-shot ones, when using properly constructed initial conditions. For higher-order flows such as v_{4,5} the single-shot simulations are shown to be incapable of reproducing those from event-by-event simulations. In Chap. 3, we show that the elliptic and triangular flow data measured by the ALICE collaboration at the LHC prefer a small specific shear viscosity close to \eta/s = 0.08, when considering the MC-Glauber and MC-KLN models. In order to allow for a much larger \eta/s value, the initial condition model must feature triangularity values ~50% larger than the ones provided by the MC-Glauber and MC-KLN models. Chap. 4 focuses on correlations between event-plane angles. We show that the event-plane angle correlation measurements by the ATLAS collaboration can be explained by hydrodynamic simulations. The same correlation patterns cannot be explained directly from the initial conditions. In Chap. 5, we show that including only ~20 out of 319 carefully chosen resonance (open full item for complete abstract)
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    Committee: Ulrich Heinz (Advisor); Yuri Kovchegov (Committee Member); Eric Braaten (Committee Member); Chris Hammel (Committee Member) Subjects: Physics