Mechanical Engineering Commons^™

Experimental And Numerical Study Of Endwall Film Cooling, Srikrishna Mahadevan

Electronic Theses and Dissertations

This research work investigates the thermal performance of a film-cooled gas turbine endwall under two different mainstream flow conditions. In the first part of the research investigation, the effect of unsteady passing wakes on a film-cooled pitchwise-curved surface (representing an endwall without airfoils) was experimentally studied for heat transfer characteristics on a time-averaged basis. The temperature sensitive paint technique was used to obtain the local temperatures on the test surface. The required heat flux input was provided using foil heaters. Discrete film injection was implemented on the test surface using cylindrical holes with a streamwise inclination angle of 35? and …

Thermodynamic Analysis And Optimization Of Supercritical Carbon Dioxide Brayton Cycles, Mahmood Mohagheghi

Electronic Theses and Dissertations

The power generation industry is facing new challenging issues regarding accelerating growth of electricity demand, fuel cost and environmental pollution. These challenges accompanied by concerns of energy resources becoming scarce necessitate searching for sustainable and economically competitive solutions to supply the future electricity demand. To this end, supercritical carbon dioxide (S-CO2) Brayton cycles present great promise particularly in high temperature concentrated solar power (CSP) and waste heat recovery (WHR) applications. With this regard, this dissertation is intended to perform thorough thermodynamic analyses and optimization of S-CO2 Brayton cycles for both of these applications. A modeling tool has been developed, which …

Inverse-Consistent Determination Of Young's Modulus Of Human Lung, Behnaz Seyfi Noferest

Electronic Theses and Dissertations

Human lung undergoes respiration-induced deformation due to sequential inhalation and exhalation. Accurate determination of lung deformation is crucial for tumor localization and targeted radiotherapy in patients with lung cancer. Numerical modeling of human lung dynamics based on underlying physics and physiology enables simulation and virtual visualization of lung deformation. Dynamical modeling is numerically complicated by the lack of information on lung elastic behavior, structural heterogeneity as well as boundary constrains. This study integrates physics-based modeling and image-based data acquisition to develop the patient-specific biomechanical model and consequently establish the first consistent Young's modulus (YM) of human lung. This dissertation has …

Droplet Impact On Liquid Pools: Secondary Droplets Formation From Rayleigh Jet Break-Up And Crown Splash, Eduardo Castillo Orozco

Electronic Theses and Dissertations

This work aims to study the impact of a droplet on liquid pools of the same fluid to understand the formation of secondary drops from the central jet and crown splash that occur after the impact. The impact of droplets on a deep pool has applications in cleaning up oil spill, spray cooling, painting, inkjet printing and forensic analysis, relying on the changes in properties such as viscosity, interfacial tension and density. Despite the exhaustive research on different aspects of droplet impact, it is not clear how liquid properties can affect the instabilities leading to the Rayleigh jet breakup and …

Development Of 3d Vision Testbed For Shape Memory Polymer Structure Applications, Kenneth Thompson

Electronic Theses and Dissertations

As applications for shape memory polymers (SMPs) become more advanced, it is necessary to have the ability to monitor both the actuation and thermal properties of structures made of such materials. In this paper, a method of using three stereo pairs of webcams and a single thermal camera is studied for the purposes of both tracking three dimensional motion of shape memory polymers, as well as the temperature of points of interest within the SMP structure. The method used includes a stereo camera calibration with integrated local minimum tracking algorithms to locate points of interest on the material and measure …

Meshless Direct Numerical Simulation Of Turbulent Incompressible Flows, Andres Vidal Urbina

Electronic Theses and Dissertations

A meshless direct pressure-velocity coupling procedure is presented to perform Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES) of turbulent incompressible flows in regular and irregular geometries. The proposed method is a combination of several efficient techniques found in different Computational Fluid Dynamic (CFD) procedures and it is a major improvement of the algorithm published in 2007 by this author. This new procedure has very low numerical diffusion and some preliminary calculations with 2D steady state flows show that viscous effects become negligible faster that ever predicted numerically. The fundamental idea of this proposal lays on several important inconsistencies …

A Multi-Scale Cfd Analysis Of Patient-Specific Geometries To Tailor Lvad Cannula Implantation Under Pulsatile Flow Conditions: An Investigation Aimed At Reducing Stroke Incidence In Lvads, Ray Prather

Electronic Theses and Dissertations

A Left Ventricular Assist Device (LVAD) is a mechanical pump that provides temporary circulatory support when used as bridge-to-transplantation and relieves workload demand placed on a failing heart allowing for myocardia recovery when used as destination therapy. Stroke is the most devastating complication after ventricular assist device (VAD) implantation, with an incidence of 14-47% over 3-6 months. This complication due to thrombus formation and subsequent transport through the vasculature to cerebral vessels continues to limit the widespread implementation of VAD therapy. Patient-specific computational fluid dynamics (CFD) analysis may elucidate ways to reduce this risk. We employed a multi-scale model of …

Mechanism Of Hip Dysplasia And Identification Of The Least Energy Path For Its Treatment By Using The Principle Of Stationary Potential Energy, Mohammed Abdulwahab M. Zwawi

Electronic Theses and Dissertations

Developmental dysplasia of the hip (DDH) is a common newborn condition where the femoral head is not located in its natural position in the acetabulum (hip socket). Several treatment methods are being implemented worldwide to treat this abnormal condition. One of the most effective methods of treatment is the use of Pavlik Harness, which directs the femoral head toward the natural position inside the acetabulum. This dissertation presents a developed method for identifying the least energy path that the femoral head would follow during reduction. This is achieved by utilizing a validated computational biomechanical model that allows the determination of …

Theoretical And Experimental Investigation Of The Cascading Nature Of Pressure-Swirl Atomization, Pretam Choudhury

Electronic Theses and Dissertations

Pressure swirl atomizers are commonly used in IC, aero-engines, and liquid propellant rocket combustion. Understanding the atomization process is important in order to enhance vaporization, mitigate soot formation, design of combustion chambers, and improve overall combustion efficiency. This work utilizes non-invasive techniques such as ultra -speed imaging, and Phase Doppler Particle Anemometry (PDPA) in order to investigate the cascade atomization process of pressure-swirl atomizers by examining swirling liquid film dynamics and the localized droplet characteristics of the resulting hollow cone spray. Specifically, experiments were conducted to examine these effects for three different nozzles with orifice diameters .3mm, .5mm, and .97mm. …

Pressurized Metal Bellows Shock Absorber For Space Applications., John Trautwein

Electronic Theses and Dissertations

Numerous spacecraft designs exist for exploring the surfaces of planetary bodies and each have their own advantages and disadvantages. All successful landings have been made by stationary landers or wheeled rovers that rely on one-time use mechanisms, such as crushable aluminum honeycomb shock absorbers or inflatable airbags, to reduce shock loading to the spacecraft during landing. The stationary lander is the simplest type of lander, but can only take data from one location. Wheeled rovers add complexity in exchange for mobility to explore different locations. Rovers are limited by the terrain they can traverse; rovers becoming stuck have ended missions. …

Development Of Velocity Profile Generating Screens For Gas Turbine Components, Joseph Tate

Electronic Theses and Dissertations

Laboratory experiments on components of complex systems such as gas turbines require many conditions to be met. Requirements to be met in order to simulate real world conditions include inlet flow conditions such as velocity profile, Reynold's number, and temperature. The methodology to be introduced designs a velocity profile generating screen to match real world conditions through the use of perforated plates. The velocity profile generating screen is an array of jets arranged in a manner to produce sections of different solidities, a ratio of area that obstructs fluid flow compared to that of the total area. In an effort …

Dynamic Mechanical Analysis And High Strain-Rate Energy Absorption Characteristics Of Vertically Aligned Carbon Nanotube (Vacnt) Reinforced Woven Fiber-Glass Composites, Kiyun Kim

Electronic Theses and Dissertations

No abstract provided.

Probabilistic Musculoskeletal Simulation Methods To Address Intersegmental Dependencies Of The Knee, Hip, And Spine, Casey A. Myers

Electronic Theses and Dissertations

Orthropaedic clinical practice in the area of the knee, hip, and spine has benefited from the concept of regional interdependence, where interventions applied to one region can influence the outcome and function of other regions of the body that may be seemingly unrelated to the applied intervention. An understanding of the biomechanical mechanisms that describe clinical practice involving knee, hip, and spine regional interdependence can improve treatment of a wide range of pathological conditions. Improvement in this area can be particularly impactful on the outcomes of patients with total joint replacement, where pathology and compensatory strategies develop during multi-joint interactions. …

Investigation Of Transmission Loss Through Double Wall Structures With Varying Small Air Gaps Using Modal Analysis., Richard Michael Phillips 1988-

Electronic Theses and Dissertations

Noise reduction testing is completed for two single steel plate constructions with different thicknesses and for two double wall constructions with different air gap thicknesses that include the same two plates used in the single plate constructions. Results compare favorably with known theory and experimental results from previous literature. These favorable comparisons include the direct relationship between mass per unit area and transmission loss for single plate constructions, the presence of a noise reduction valley near the mass-air-mass frequency, the dependency of the mass-air-mass frequency on the air gap thickness, and the existence of a bridge frequency. Despite the similarities …

Transient Heat Transfer Between A Magnetocaloric Packed Particle Bed And Stagnant Interstitial Fluid., Michael G. Schroeder 1988-

Electronic Theses and Dissertations

In the field of magnetocaloric heat pumps, many system models have been made. What most of these models lack is heat transfer occurring while there is no fluid motion. It is the objective of this paper to analytically determine and experimentally verify heat transfer with no bulk fluid motion. The addition of a pure dwell period to the typical magnetocaloric cycle was shown to have a positive performance impact in specific conditions. These conditions correspond to regenerators that are heat transfer rate limited in operation. The heat transfer mechanism for this particular case was shown to be pure conduction via …

The Development Of A Laminated Copolyester Electric Guitar, Addison S. Karnes

Electronic Theses and Dissertations

This thesis is an investigation of the fabrication and assembly methodologies employed in the development of a proof-of-principle prototype electric guitar composed of laminated copolyester. The objective of the project was to develop the processes and procedures to create an optimized physical and visual bond between layers to minimize vibratory dissipation, thus maximizing sustain. A high speed CNC router, abrasive waterjet, laser engraver-cutter, as well as various manual fabrication and assembly methods were investigated in the construction of the guitar prototypes. The lamination processes explored include low-temperature, heat-assisted pressure bonding, solvent and chemical welding, and contact adhesives. The project concluded …

Cavitation In Vial Drop Subjected To Mechanical Shock, Houman Babazadehrokni

Electronic Theses and Dissertations

Cavitation is a phenomenon that occurs when the local pressure falls down below the critical pressure. Previous work from the Randolph lab demonstrated that protein aggregates can form when a vial of therapeutic solution is dropped onto a hard surface. The process by which this occurs is most likely shock induced cavitation. During this process, hot spots can be created with temperatures and pressures reaching thousands of Kelvin and hundreds of atmospheres, respectively, leading to degradation of protein therapeutics. This work will extend previous efforts by exploring differences generated by change in vial materials, solutions, drop methods and fill volumes. …

Nanoporous Bi2te3 Thermoelectric Based Knudsen Gas Pump., Abderrazzak Faiz

Electronic Theses and Dissertations

This dissertation reports on the fabrication of a bi-directional Knudsen gas pump using a multifunctional nanoporous thermoelectric material. The integration of the channels into the thermoelectric material has the advantages of reducing heat losses and power consumption, improving the pump efficiency, and reducing the overall pump size. The Knudsen pump operates on the thermal transpiration principle, the phenomenon that gas molecules drift from the cold end to the hot end of a narrow channel. The gas pumping is realized in the transition or free molecular regime. The Knudsen pump is needed in a great number of applications such as gas …

Photomechanical Actuation Of Liquid Crystal Nanotube Elastomers., Xiaoming Fan

Electronic Theses and Dissertations

Elastomeric composites based on nanotube liquid crystals (LCs) that preserve the internal orientation of nanotubes could lead to anisotropic physical properties and flexible energy conversion. Using simple vacuum filtration technique of fabricating nanotube LCs films and utilizing a transfer process to poly (dimethyl) siloxane wherein the LCs arrangement is preserved, in this thesis we demonstrate unique and reversible photomechanical response of this layered composite to excitation by near infra-red (NIR) light at ultra-low nanotube mass fractions. Schlieren textures were noted in these LCs composites confirming long range macroscopic nematic order of nanotubes within the composites. Maximum photomechanical stress of ~23kPa, …

Hydraulic Switch For Dishwashers With Bottle Blaster System., Lazaro Galban

Electronic Theses and Dissertations

A dishwasher works by using water pressure to operate the Spray Arms. There are different types of wash systems with the most common being two spray arms, a lower and middle arm. These two spray arms operate independently from each other and can be powered individually. In this particular wash system, the subsystem of interest is the Mid Spray Arm which is connected with the Bottle Blaster where both operate simultaneously. The Mid Spray Arm is used to clean the upper dishwasher rack while the Bottle Blaster is used to clean bottles, also in the upper rack. In order to …

The Second Generation Of The Cccm System For In-Vitro Cardiac Tissue Engineering., Mai-Dung Thi Nguyen

Electronic Theses and Dissertations

Cardiovascular disease is the leading cause of death worldwide. When a myocardial infarction occurs, scar tissue compensates the damaged myocardial tissue. This scar tissue increases the stiffness of the heart tissue, reduces the heart’s function, and finally leads to the heart failure (HF) disease. To have the tissue engraftment, in-vitro cardiac tissue should have the same properties as the native mature cardiac tissue. However, current in-vitro cell culture technologies fail to accurately recreate the in-vivo like mechanically physiological environment for in-vitro cardiac tissue culture, and therefore, fail to regenerate the in-vivo like mature cardiac tissue. Hence, a microfluidic cardiac cell …

Numerical Investigation Of Hydrodynamic Focusing And Coulter Principle In A Microfluidic Device, Muheng Zhang

Electronic Theses and Dissertations

Particle information such as particle size and amount is significant to many fields such as chemical engineering, biological research, medical analysis, and environment detection. Microfluidic Coulter counter is suitable for this task because it can get fast and accurate analysis. However, the fundamental principle and several design strategies details are still needed to be analyzed and modeled in order to improve its performance. This dissertation focused on several challenges from the numerical simulation aspects. First one is the analysis for the hydrodynamic focusing in microfluidic Coulter Counter. In recent years, many microfluidic Coulter Counter designs have utilized a technique termed …

Numerical Study Of Leading Edge Vortex Circulation Development On Finite Aspect Ratio Perching Wings., Kyle Hord

Electronic Theses and Dissertations

The perching maneuver of natural fliers is a complex motion involving fast change of angle of attack, complicated wing kinematics, large wing deformation and agile body motion control, but the prominent aerodynamic features can be revealed using a simple pitch-up wing motion coupled with a stream wise deceleration. In this dissertation the aerodynamic forces, the leading edge vorterx (LEV) development, and LEV circulation of pitch-up and perching wings are extensively studied at low Reynolds number conditions. 2D and 3D wings of different aspect ratios were linearly pitched up from 0 to 90 at three reduced pitch rates. The numerical investigation …

Stress Corrosion Cracking In Polymer Matrix Glass Fiber Composites, Jonathan Kosak

Electronic Theses and Dissertations

With the use of Polymer Matrix Glass Fiber Composites ever expanding, understanding conditions that lead to failure before expected service life is of increasing importance. Stress Corrosion Cracking (SCC) has proven to be one such example of conditions found in use in high voltage transmission line applications that leads to brittle fracture of polymer matrix composites.

SCC has been proven to be the result of acid buildup on the lines due to corona discharges and water buildup. This acid leaches minerals from the fibers, leading to fracture at low loads and service life. In order to combat this problem, efforts …

Advancements In Alternative Energy Applications For Space Conditioning., Brian S. Robinson

Electronic Theses and Dissertations

This dissertation documents advancements made in passive, renewable energy applications for building space conditioning (heating and cooling). Since, for most climates across the US, space heating requires a much larger annual energy demand than space cooling, the majority of this dissertation is focused on the heating season. The dissertation is divided into five chapters, primarily covering computer simulations and experimental studies pertaining to specific space conditioning technologies. Chapter One discusses the significance of supplanting fossil fuel based energy production with clean, renewable sources, and provides further detail on the organization of this dissertation. Chapter Two provides background on the heat …

Development And Evaluation Of A Calibration Free Exhaustive Coulometric Detection System For Remote Sensing., Thomas James Roussel

Electronic Theses and Dissertations

Most quantitative analytical measurement techniques require calibration to correlate signal with the quantity of analyte. The purpose of this study was to employ exhaustive coulometry, an implementation of coulometric analysis in a stopped-flow, fixed-volume, thin-layer cell, to attain calibration-free measurements that would directly benefit intervention-free analysis systems designed for remote deployment. This technique capitalizes on the short diffusion lengths (< 100 µm) to dramatically reduce the time for analysis (< 30 sec). For this work, a thin-layer fluidic cell was designed in software, fabricated via CNC machining, and evaluated using Ferri/Ferrocyanide {Fe(CN)63-/4-} as a model analyte. The 2 µL fixed volume incorporated an oval, 8mm by 4 mm, thin-film gold electrode sensor with an integrated Ag|AgCl pseudo-reference electrode. The flow cell area matched the shape of the sensor, with a volume set by the thickness of a laser-cut silicone rubber gasket (~80 µm). A semi-permeable membrane isolated the working electrode and counter electrode chambers to prevent analyte diffusion. A miniaturized custom potentiostat was designed and built to measure reaction currents ranging from 10 mA to 0.1 nA. Software was developed to perform step voltammetry as well as cyclic voltammetry analysis for verifying electrode condition and optimal redox potential levels. Experimentally determined oxidation/reduction potentials of -100 mV and 400 mV, respectively, were applied to the working electrode for sample concentrations ranging from 50 µM to 10,000 µM. The current generated during the reactions was recorded and the total charge captured at each concentration was obtained by integrating the amperograms. When compared to the expected charge for a 2 µL sample, the total charge vs. concentration plots displayed a near perfect linearity over the full concentration range, and the expected charge (100 % converted) was reached within 20 seconds. The reaction currents ideally should have decayed to background levels, but exhibited constant offset values slightly larger than the background signal, a phenomenon assumed to be lingering residual flow from sample injection. After adding rigid tubing and external valves, the thin-layer cell was shown to remain within 6% of the theoretical charge after 200 seconds. Continued development of this system will offer the possibility of remote, calibration-free determinations of real-world analytes such mercury and lead.

Design And Evaluation Of A Propulsion System For Small, Compact, Low-Speed Maneuvering Underwater Vehicles, Florence M. Mbithi

Electronic Theses and Dissertations

Underwater vehicles used to perform precision inspection and non-destructive evaluation in tightly constrained or delicate underwater environments must be small, have low-speed maneuverability and a smooth streamlined outer shape with no appendages. In this thesis, the design and analysis of a new propulsion system for such underwater vehicles is presented. It consists primarily of a syringe and a plunger driven by a linear actuator and uses different inflow and outflow nozzles to provide continuous propulsive force. A prototype of the proposed propulsion mechanism is built and tested. The practical utility and potential efficacy of the system is demonstrated and assessed …

Computational Fluid Dynamics Uncertainty Analysis For Payload Fairing Spacecraft Environmental Control Systems, Curtis Groves

Electronic Theses and Dissertations

Spacecraft thermal protection systems are at risk of being damaged due to airflow produced from Environmental Control Systems. There are inherent uncertainties and errors associated with using Computational Fluid Dynamics to predict the airflow field around a spacecraft from the Environmental Control System. This paper describes an approach to quantify the uncertainty in using Computational Fluid Dynamics to predict airflow speeds around an encapsulated spacecraft without the use of test data. Quantifying the uncertainty in analytical predictions is imperative to the success of any simulation-based product. The method could provide an alternative to traditional “validation by test only” mentality. This …

Computational Fluid Dynamics Simulation Of United Launch Alliance Delta Iv Hydrogen Plume Mitigation Strategies, Stephen Guimond

Electronic Theses and Dissertations

During the launch sequence of the United Launch Alliance Delta IV launch vehicle, large amounts of pure hydrogen are introduced into the launch table and ignited by Radial-Outward-Firing-Igniters (ROFIs). This ignition results in a significant flame, or plume, that rises upwards out of the launch table due to buoyancy. The presence of the plume causes increased and unwanted heat loads on the surface of the vehicle. A proposed solution is to add a series of fans and structures to the existing launch table configuration that are designed to inject ambient air in the immediate vicinity of the launch vehicle's nozzles …

Piezospectroscopic Calibration Of Alumina-Nanocomposites For The Development Of Stress-Sensing Structures, Daniela Fugon-Dessources

Electronic Theses and Dissertations

Alpha-alumina is known to exhibit photo-luminescent (PL) properties, mainly characteristic R-lines that shift according to applied stress. In addition to showing excellent PL properties, polymers with embedded alumina nanoparticles have been shown to improve the overall composite mechanical properties. While the use of the PL properties to develop stress-sensing materials using an alumina-epoxy material has been success- fully shown in compression, the properties have not been developed for tension. In this study, the PL response of variable volume fraction alumina-epoxy composites will be determined under tensile conditions. It is expected that increasing the volume fraction of alumina nanoparticles will increase …