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Full-Text Articles in Mechanical Engineering
Rotational And Shower Head Cooling Hole Effects On Leading-Edge Jet Impingement Heat Transfer, Weston Olson
Rotational And Shower Head Cooling Hole Effects On Leading-Edge Jet Impingement Heat Transfer, Weston Olson
Electronic Theses and Dissertations, 2020-
Jet Impingement and shower head cooling are critical cooling techniques used to maintain turbine blades at operational temperatures. Jet impingement is extremely effective at removing large amounts of heat flux from the target surface, the inner blade wall, through stagnation point heat transfer. Shower head cooling produces a cooling film around the exterior of the blade, in return reducing external heat flux. The current work consisted of investigating the jet impingement effectiveness with rotational effects for two different cooling schemes. The analysis was conducted numerically using STAR CCM+ with two different turbulence models, the three equation Lag Elliptic Blending K …
Production And Elastomer Compatibility Of Renewable Fuels, Alan Felix
Production And Elastomer Compatibility Of Renewable Fuels, Alan Felix
Electronic Theses and Dissertations, 2020-
Hydrocarbon fuel plays an essential role in modern day society and significant research effort is put forth for fuel characterization, performance optimization, and new procedures for synthesis. Despite the eventual and inevitable shift away from hydrocarbon fossil fuels to more renewable energies, investigations into liquid hydrocarbons remain useful while governments slowly adopt and integrate alternative energies. Many hydrocarbon fuel alternatives can potentially bridge the gap between today's heavy reliance on fossil fuels and future complete adaptation of clean energy. One such alternative is biofuel, which is still hydrocarbon based but is made from bio-materials, most notably plants. Widespread use of …
A Computational Biomechanical Model-Based Optimization Of Fulcrum Support In Orthosis Enabled Closed Reduction Of Developmental Dysplasia Of The Hip, Christopher Rose
A Computational Biomechanical Model-Based Optimization Of Fulcrum Support In Orthosis Enabled Closed Reduction Of Developmental Dysplasia Of The Hip, Christopher Rose
Electronic Theses and Dissertations, 2020-
Hip abduction orthosis devices (HAOD) are used to reduce the hip joint of infants affected by developmental dysplasia of the hip (DDH). HAOD have been successful for mild cases of DDH and ineffective for severe cases. Efforts in understanding the biomechanics of lower limbs have been made to improve the success rate of current treatment methods, especially for Grade IV dislocations (G4). The aim of this dissertation is twofold: first, it proposes the use of a varying fulcrum point (FP) located below the leg to improve DDH treatment; and secondly, it defines the optimal FP (OP) location for a broad …
Engineering The Surface Chemistry And Surface Conditions To Optimize The Heat Removal Rate Of Various Surfaces, Thomas Germain
Engineering The Surface Chemistry And Surface Conditions To Optimize The Heat Removal Rate Of Various Surfaces, Thomas Germain
Electronic Theses and Dissertations, 2020-
As the demand for more powerful and smaller electronics rise, the need for creative cooling solutions to prevent burnout becomes increasingly paramount. In response to recent cooling needs, new cooling techniques, such as jet impingement cooling, spray cooling, and heat pipes, have risen in popularity for their simple design and efficiency in thermal transport. This interest has risen in both industry and academia, where research has been conducted to optimize the heat transfer performance for these systems and how these systems can be implemented in new technologies. One method that has risen in interest is affecting the surface, through physical …
Experimental Investigation Of The Laminar Burning Velocities Of High-Performance Co-Optima Biofuels, Gihun Kim
Experimental Investigation Of The Laminar Burning Velocities Of High-Performance Co-Optima Biofuels, Gihun Kim
Electronic Theses and Dissertations, 2020-
Co-Optimization of Fuels and Engines (Co-Optima) initiative of the U.S Department of Energy (DOE) started research on biofuel and biodiesel to replace the gasoline (petrol) and diesel for over the road internal combustion engines. From an initial list of thousands of fuels, selected bio-fuels and biodiesels were investigated for further combustion studies following the implementation of screening, which consisted of biodegrading, toxicity, flash point, research octane number, motor octane numbers, cetane number, and economic effect, etc. Experimental measurements of laminar burning velocity (LBV) are key parameters to understand fuel performance and applicability in engines. Furthermore, knowledge of LBV is required …
Experimental, Analytical And Computational Analyses Of Linear And Radial Shape Memory Alloy Helical Actuators, Ryan Puchaty
Experimental, Analytical And Computational Analyses Of Linear And Radial Shape Memory Alloy Helical Actuators, Ryan Puchaty
Electronic Theses and Dissertations, 2020-
As access to Shape Memory Alloys (SMAs) has expanded beyond their use as linear wires, the need for characterizing more complex forms that account for the effects of multi-axial stress, strain, and displacement has become increasingly important in actuator design. The novel uses of SMA actuators have also moved the devices into previously unexplored loading conditions, where established theory does not adequately model the real behavior. This work seeks to alleviate some of these issues by addressing problems with the most common multi-axial stress devices: helical springs. New applications are requiring high forces in small spaces, where SMAs' high work …
Pathological Tremor As A Mechanical System: Modeling And Control Of Artificial Muscle-Based Tremor Suppression, Christopher Kelley
Pathological Tremor As A Mechanical System: Modeling And Control Of Artificial Muscle-Based Tremor Suppression, Christopher Kelley
Electronic Theses and Dissertations, 2020-
Central nervous system disorders produce the undesired, approximately rhythmic movement of body parts known as pathological tremor. This undesired motion inhibits the patient's ability to perform tasks of daily living and participate in society. Typical treatments are medications and deep brain stimulation surgery, both of which include risks, side effects, and varying efficacy. Since the pathophysiology of tremor is not well understood, empirical investigation drives tremor treatment development. This dissertation explores tremor from a mechanical systems perspective to work towards theory-driven treatment design. The primary negative outcome of pathological tremor is the undesired movement of body parts: mechanically suppressing this …
Cell Encapsulation In Microfluidic Channels, Mohammad Nooranidoost
Cell Encapsulation In Microfluidic Channels, Mohammad Nooranidoost
Electronic Theses and Dissertations, 2020-
Droplet Microfluidics can be utilized to control the production of single droplets and double emulsions in biomedical application. This dissertation analyzes the droplet formation in hydrophobic and hydrophilic microchannels, encapsulation of cells in flow-focusing channels, and deformation of cell-laden droplets in constricted microcapillaries. The formation of droplets is studied in hydrophobic and hydrophilic channels in order to investigate the role of contact angle on flow structures and droplet generation patterns. In the hydrophobic case, stable and well-structured droplet and slug generation is achieved. However, the flow structure in the hydrophilic case significantly depends on contact angles of the walls. A …
Study On Comprehensive Mechanical Properties Of Metallic Matrix Cnt Nano-Composites, Shutao Song
Study On Comprehensive Mechanical Properties Of Metallic Matrix Cnt Nano-Composites, Shutao Song
Electronic Theses and Dissertations, 2020-
Carbon nanotubes (CNT) have excellent mechanical strengths, electrical conductivity, and thermal conductivity. CNT reinforced metallic nano-composites are viewed as a great candidate to replace traditional alloy materials. It has been shown that CNTs can greatly enhance the strength, thermal conductivity, and electrical conductivity of composites. However, the ductility of composites would deteriorate due to the addition of CNTs if the fabrication or/and processing methods are not improved or well designed. This dissertation investigated (1) the strengthening mechanisms of CNT on metallic matrix, such as mechanical strength and thermal conductivity, and (2) analytical modeling on the strength-ductility trade-off of CNT reinforced …
Interfacial Properties Modulate Water Entry Dynamics For Spherical Projectiles, Daren Watson
Interfacial Properties Modulate Water Entry Dynamics For Spherical Projectiles, Daren Watson
Electronic Theses and Dissertations, 2020-
Rigid bodies impacting liquid pools incite splashing and air-entraining cavities that depend on impactor shape, entry speed, surface texture, and free surface conditions. In this body of work, we investigate the influence of interfacial properties on water entry dynamics for free-falling spherical projectiles. Our investigations translate to everyday fluid-structure interactions that are complex and generally conclude beyond the temporal acuity of the naked eye. High-speed videography between 1000 -- 3200 fps is used to digitize the water entry process and measure salient splash features under different initial conditions. We assess splashes arising from the impacts of free-falling hydrophilic spheres with …
Multi-Species Measurements At High Temperatures Using Advanced Mid-Infrared Laser Schemes, Zachary Loparo
Multi-Species Measurements At High Temperatures Using Advanced Mid-Infrared Laser Schemes, Zachary Loparo
Electronic Theses and Dissertations, 2020-
High-temperature reacting systems are central to many fields including propulsion, power generation, and transportation. Studying such systems requires the use of experimental facilities such as shock tubes to obtain the relevant high temperature conditions, and non-intrusive diagnostic tools for monitoring parameters of interest in the reaction zone, including temperature and species concentration time-histories. Laser absorption spectroscopy offers high-speed, in-situ measurements of the reacting flow field and provides direct measurements of species concentrations and temperature. Applying absorption spectroscopy via different diagnostic strategies enables tailored measurements of these parameters across a variety of combustion systems for chemical kinetic model refinement and enhancing …
A Shock Tube Chemical Kinetic Study Of Ethanol Oxidation At Elevated Pressures, Andrew Laich
A Shock Tube Chemical Kinetic Study Of Ethanol Oxidation At Elevated Pressures, Andrew Laich
Electronic Theses and Dissertations, 2020-
Understanding the combustion chemistry of ethanol is critical for continued proliferation and use in future internal combustion engines (ICEs) that will operate in a downsized, turbo-charged, high compression configuration. Detailed chemical kinetic reaction mechanisms already exist for ethanol, which have been validated over a range of operating conditions; however, capturing the conditions that may be seen in future ICEs requires extension of these conditions, namely at elevated pressure. Investigating the kinetics of ethanol existing in a combustion system first involve, for example, understanding a key global metric like ignition delay time (IDT) and measuring major or minor species in a …
Classical Engineering Systems Provide Behavioral Analog For Ephemeral Insect And Plant Biomechanics, Nicholas Smith
Classical Engineering Systems Provide Behavioral Analog For Ephemeral Insect And Plant Biomechanics, Nicholas Smith
Electronic Theses and Dissertations, 2020-
In this dissertation we consider ephemeral behaviors of two small-scale living systems, mosquitoes and citrus fruit reservoirs. While these two systems share few obvious commonalities, they both express life events that are complex and conclude within approximately 50 milliseconds. We utilize high-speed videography, between 1,000-16,000 fps, to detail how complex behavior can be modeled as classical engineering systems. Beginning with the larger organism we assessed the landing and takeoff behavior of Aedes aegypti mosquitoes to ascertain the secrets of their covert interaction with humans. At takeoff, mosquitoes decrease pushing contact time with substrates of low friction through a modified takeoff …
Seismocardiographic Signal Variability And Pulmonary Phase Detection In Adults, Md Khurshidul Azad
Seismocardiographic Signal Variability And Pulmonary Phase Detection In Adults, Md Khurshidul Azad
Electronic Theses and Dissertations, 2020-
Cardiovascular disease is one of the leading causes of mortality in the world. Early detection and intervention can significantly improve disease management and patient quality of life. Current methods of evaluating cardiac function often involve history and physical examination (including stethoscope auscultation), electrocardiograms (ECG), echocardiogram imaging, computed tomography, and various blood tests. Seismocardiographic signals (SCG) are the chest surface vibrations resulting from cardiomechanical activity. SCG may be recorded using accelerometers and can be used for monitoring and predicting cardiac health. SCG's potential utility may be impeded by its spatial, postural, respiratory, and longitudinal variability. In this dissertation, the SCG variability …
Design Of An Annular Disc-Shaped Heat Pipe For Air-Cooled Steam Condensers, Ahmad Saleh
Design Of An Annular Disc-Shaped Heat Pipe For Air-Cooled Steam Condensers, Ahmad Saleh
Electronic Theses and Dissertations, 2020-
Limitations on water utilization are turning into an expanding issue for the power and electricity generation industry. As a contribution to the solution of water consumption problems, utility companies are shifting toward using air-cooled condensers (ACC) in replace to the typical water-cooling methods of once-through cooling and the surface condenser/wet-cooling tower combination. Although the ACC is a dry cooling method, the industry is quite hesitant to switch over to ACC mainly for three reasons: (a) lower power output, (b) higher capital cost, and (c) larger physical footprint. All these drawbacks are because of the high overall thermal resistance of condensing …
Study On Ductile Fracture With Anisotropic And Strain Rate Effects In Manufacturing Processes, Hao Pan
Study On Ductile Fracture With Anisotropic And Strain Rate Effects In Manufacturing Processes, Hao Pan
Electronic Theses and Dissertations, 2020-
Ductile fracture is a topic of great importance in automotive and aerospace industries. Prediction of ductile fracture in engineering structures relies on developing robust material models under complex loading conditions. This dissertation addresses the anisotropic and strain rate effects in constitutive and ductile fracture models of lightweight metals. In the present modeling framework, the anisotropic plasticity behavior is modeled by combination of an initial anisotropic yield function and an isotropic hardening correction by Lode dependence. A new all-strain based anisotropic fracture model is proposed based on the approach of linear transformation on plastic strain rate tensor. The strain rate effects …
Heat Transfer And Correlations Of Jet Array Impingement With Flat And Pimple-Dimpled Plate, Husam Nizar Ahmad Zawati
Heat Transfer And Correlations Of Jet Array Impingement With Flat And Pimple-Dimpled Plate, Husam Nizar Ahmad Zawati
Electronic Theses and Dissertations, 2020-
This study compares and analyses the heat transfer between a novel jet array impingement configuration (designated as NPR) and a baseline jet orifice plate (flat) in a maximum crossflow scheme. Both jet plates feature inline arrays of 20 x 26 circular air jets that orthogonally impinge on a flat target surface consisting of 20 segments, parallel to the jet plates. The NPR plate consists of staggered semi-spherical pimples (protrusions) and dimples (imprints) with a jet-to-pimple diameter ratio (Dj,p/Dp) of 0.07 and jet length-to-pimple diameter ratio (L/Dj,p) of ~ 1 with a protrusion ratio (tp/Dj,p) of 2.78. The dimples (imprints) have …
Supercritical Co2 Heat Transfer Study Near Critical Point In A Heated Circular Pipe, Akshay Khadse
Supercritical Co2 Heat Transfer Study Near Critical Point In A Heated Circular Pipe, Akshay Khadse
Electronic Theses and Dissertations, 2020-
Supercritical CO2 (sCO2) power cycle is an up-and-coming technology to produce electricity from various heat sources. Apart from power cycles, sCO2 can also be used as coolant in centralized cooling system and stand-alone cooling device. However, lack of accurate predication tools such as heat transfer coefficient correlations and insufficient knowledge behind fundamental heat transfer processes can hinder its practical realization in key energy and cooling systems. The overall objective of the study is to extend fundamental knowledge about heat transfer and fluid flow processes in conduits pertinent to sCO2 power cycle. The emphasis here is investigation of heat transfer effects …
High-Speed Imaging Of Reflected Shockwave-Initiated Combustion, Erik Ninnemann
High-Speed Imaging Of Reflected Shockwave-Initiated Combustion, Erik Ninnemann
Electronic Theses and Dissertations, 2020-
Shock tubes are considered ideal reactors and are used extensively to provide valuable chemical kinetic measurements, such as ignition delay times and in-situ species time-histories. However, due to nonideal affects the combustion of fuel inside shock tubes can become nonhomogeneous, particularly at low temperatures, which complicates the acquired data. In this work, the combustion of practical fuels used by society are investigated with high-speed imaging. First, high-speed images were captured through the end wall of the shock tube for two hydrogen-oxygen systems. The combustion process was found to initiate in two modes, one that is homogeneous across the fluid medium …
Additive Manufacturing Of Elastomeric Lung Phantoms In Radiation Oncology, Jonathan Sookdeo
Additive Manufacturing Of Elastomeric Lung Phantoms In Radiation Oncology, Jonathan Sookdeo
Electronic Theses and Dissertations, 2020-
Cancer is a particularly difficult disease to manage and treat, with cancer of the lung being a notably complex disease to treat with radiation therapy. In this study, a stereolithography-based 3D printing process was developed to fabricate human lung phantoms with identical mechanical and physical properties of human lungs in order to assist with targeted radiation therapy. A highly flexible UV photopolymer material with an elastic modulus of approximately 350 KPa was formulated for use in a custom-built stereolithography-based 3D printing apparatus. The printer built for 3D printing of the photopolymer features a large build volume with off-shelf components with …
Contact Mechanics Of Fish Scale Inspired Exoskeletal Components On A Nonlinear Elastic Substrate, Jeremy Stephen
Contact Mechanics Of Fish Scale Inspired Exoskeletal Components On A Nonlinear Elastic Substrate, Jeremy Stephen
Electronic Theses and Dissertations, 2020-
The contact mechanics of structures with exoskeletal components deviate significantly from classical Hertzian and non-linear models. In the case of fish scale inspired samples under blunt indentation loading these factors are inherently tied to both the size of the indenter and the scales' distribution and orientation. Control of these geometric parameters provides a pathway to tailor the properties of surfaces for better grip, damage mitigation and controlled deformation. This study explores the response of a substrate with stiff scales protruding from its surface, which is comprised of a soft elastomeric material with properties typical of those in soft robotics applications. …
Detailed Study Of Flow And Surface Heat Transfer Enhancement Mechanism In The Presence Of Dimples And/Or Protrusions, Gaurav Gupta
Detailed Study Of Flow And Surface Heat Transfer Enhancement Mechanism In The Presence Of Dimples And/Or Protrusions, Gaurav Gupta
Electronic Theses and Dissertations, 2020-
Recent advancements in material technology have led to the development of non-porous negative Poisson's ratio (NPR) materials (also called auxetic structures) by making spherical inline dimples on both sides of an elastic sheet. Manufacturing technologies such as 3-D printing and additive manufacturing paved the way to realize the complex shapes needed to achieve NPR behavior. These materials are desirable in many engineering applications, especially in the gas turbines hot-gas-path, due to their unique properties. In the current study, an effort is made to understand the flow physics and surface heat transfer mechanism for channel flow having one wall with spherical …
Molecular Dynamics Simulation Study On Thermal Conduction Of Cnt-Cu/Al Composites With New Meam Potentials Between C And Cu/Al, Luyang Ren
Electronic Theses and Dissertations, 2020-
Carbon nanotubes (CNTs) have been a promising material for thermal management applications including micro/nano-electromechanical system (MEMS/NEMS) due to their extremely high thermal conductivity values. CNTs-reinforced Cu/Al (CNT-Cu/Al) composites are attractive to meet all-around requirements on high thermal performance materials to be applied in many areas, such as aerospace, automotive and electronic packaging. However, the experimental results on resultant thermal conductivity of these composites are far from expectation due to the law of mixture. In this research, molecular dynamics (MD) simulation is used to study the thermal conduction of CNT-Cu/Al composites. Before the simulation is conducted, new inter-atomic potentials for the …
Tip Clearance Effect On Convective Heat Transfer In Micro Scale Pin Fins, Hanieh Tabkhivayghan
Tip Clearance Effect On Convective Heat Transfer In Micro Scale Pin Fins, Hanieh Tabkhivayghan
Electronic Theses and Dissertations, 2020-
Fluid flow and local heat transfer in a microchannel with single and array of pin fins have been studied. For the single pin fin case, a microchannel with a 150-µm diameter pin fin with a tip clearance was experimentally and numerically studied for three Reynolds numbers in laminar regime. Tip clearances of 0, 30, 45 and 100 µm in a 200-µm high microchannel. Experimental and numerical local temperatures and the corresponding Nusselt numbers along the centerline of the pin fin were presented and discussed. Local temperatures were measured on top of the heater surface and downstream the pin fin through …
Seismocardiography - Genesis, And Utilization Of Machine Learning For Variability Reduction And Improved Cardiac Health Monitoring, Peshala Thibbotuwawa Gamage
Seismocardiography - Genesis, And Utilization Of Machine Learning For Variability Reduction And Improved Cardiac Health Monitoring, Peshala Thibbotuwawa Gamage
Electronic Theses and Dissertations, 2020-
Seismocardiography (SCG) is the measured chest surface vibrations resulting from cardiac activity. Although SCG can contain information that correlate with cardiac health, its utility may be limited by lack of understanding of the signal genesis and a variability that can mask subtle SCG changes. The current research utilized medical imaging reconstruction and finite element method (FEM) to simulate SCG by modeling the propagation of myocardial movements to the chest surface. FEM analysis provided a link between myocardial movements and the SCG signals measured at the chest surface and suggested that myocardial movement is a primary source of SCG. Increased understanding …
High-Speed Interferometry And Visible Videography For Meniscus Curvature Analysis During Anisotropic Hemiwicking, John Bal
Electronic Theses and Dissertations, 2020-
Recent advancements in microelectronics have increased the need for thermal management systems capable of high heat flux dissipation within significant spatial constraints. One method of increasing local heat fluxes is the fabrication of superhydrophilic materials via micro/nanostructuring of the surface. Superhydrophilic surfaces act in a self-pumping capacity, spreading fluid beyond its intrinsic meniscus length to form thin-films, a process known as "hemiwicking", with practical applications in evaporative cooling, as well as flow, pool, and thin-film boiling. Of particular interest is anisotropic hemiwicking via asymmetric microstructuring. The microscopic asymmetricity of the design induces a macroscopically preferred direction of wicking, which has …