Mechanical Engineering Commons^™

Temperature Dependence Of Shear Speed In Micellar Fluid, E.G. Sunethra Kumari Dayavansha

Electronic Theses and Dissertations

Wormlike micellar (WM) fluids are viscoelastic and can support shear waves. Phase transitions of the micellar aggregates are temperature dependent and can manifest as sharp changes in the shear wave speed as a function of temperature. Thus, shear waves provide a good tool for detecting the existence of phase transitions. In this work, the variation of shear speed with temperature of 200mM CTAB/NaSal micellar fluid in a 5:3 ratio was studied. The dependence of shear wave speed on time between fluid synthesis and measurement was also investigated. Shear wave propagation through the fluid was observed as a time varying birefringence …

Zrb2-Sic Based Ultra High Temperature Ceramic Composites: Mechanical Performance And Measurement And Design Of Thermal Residual Stresses For Hypersonic Vehicle Applications, Richard Stadelmann

Electronic Theses and Dissertations

Ultra-high temperature ceramics (UHTCs), such as ZrB2-based ceramic composites, have been identified as next generation candidate materials for leading edges and nose cones in hypersonic air breathing vehicles. Mechanical performance of ceramic composites play an important role in the ultra-high temperature applications, therefore SiC is added to ZrB2 as a strengthening phase to enhance its mechanical performance. The high melting temperatures of both ZrB2 and SiC, as well as the ability of SiC to form SiO2 refractory oxide layers upon oxidation make ZrB2-SiC ceramics very suitable for aerospace applications. Thermal residual stresses appearing during processing are unavoidable in sintered ZrB2-SiC …

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.

Fiber Compaction And Wetout In Tapered Resin Injection Pultrusion Manufacturing, Naveen Babu Masuram

Electronic Theses and Dissertations

Pultrusion is a continuous process for manufacturing composite materials with constant cross section. Reinforced fibers are pulled through a resin, possibly folloby a separate injection chamber preforming system, and into a heated die, where the resin undergoes complete wetout. Thus the required pultruded composite is obtained in the desired profile. The main objective of this research is to present a numerical model employing the finite volume technique to simulate the resin flow in a tapered injection chamber through the fiber reinforcement when compaction of the fiber reinforcement is taken into account. The numerical model predicts the impact of design and …

Some Experimental Investigation On Effect Of Light And Vibration On Nano Coated Piezo For Energy Harvesting, Abhay Sharma

Electronic Theses and Dissertations

PZT is a promising piezoelectric ceramic material which has a wide range of applications in a variety of fields such as acoustic sensors and transducers, electrical switches, medical instrumentation, artificial sensitive skin in robotics, automotive detection on roads, nondestructive testing , structural health monitoring and as a biocompatible material. In this research a cantilever based multi energy harvester was developed to maximize the power output of PZT sensor. Nano mixtures containing graphene, ferrofluid nanoparticle (FNP) and ZnO nano particles were used to enhance the piezoelectric and photovoltaic output of the sensor. The samples were tested under different energy conditions to …

Spray Deposition Modeling Of Carbon Nano-Inks, John Sparkman

Electronic Theses and Dissertations

Carbon nanopaper (CNP) exhibits qualities that are desirable for a number of applications such as flame retardancy, lightning protection, and flexible printed circuit boards. CNP has become a desired engineering material in many important sectors of industries such as space, automotive, aviation, and military. However the production of consistent thicknesses and dispersion remains a challenge for practical use. Most of the standard methods of production do not allow for continuous applications or digital fabrication of the CNP. In this work, CNP is produced two different ways that allows for continuous production and digital fabrication. The continuous CNP making technique uses …

Analysis Of Steady State Micro-Droplet Evaporation To Enhance Heat Dissipation From Tiny Surfaces., Harish Voota

Electronic Theses and Dissertations

Experimental investigations and numerical predictions of steady state microdroplet evaporation experiments are presented. Steady state droplet evaporation experiments are conducted to understand (1) Droplet contact line influence on evaporation rate efficiency, (2) Droplet contact angle correlation to evaporation rate and (3) Substrate cooling. Experiments are performed on a polymer substrate with a moat like trench (laser patterned) to control droplet contact line dynamics. A bottom-up methodology is implemented for droplet formation on the patterned substrate. Droplet evaporation rates on substrate temperatures 22°C≤ ∆TSubstrate ≤75°C and contact angles 80°≤ Θ ≤110° are measured. For a pinned microdroplet (CCR), volumetric infuse rate …

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. …

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 …

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 …

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. …

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 …

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 …

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, …

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 …

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 …

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 …