Mechanical Engineering Commons^™

Knee Articular Cartilage Material Properties Estimation Through Fea, Eduardo Enrique Valdez

Graduate College Dissertations and Theses

Osteoarthritis (OA) is a debilitating disease that leads to disability and loss of quality of life. Post-traumatic osteoarthritis (PTOA) is a version of OA that develops after acute injury to the knee. PTOA is of particular interest because the disease can manifest earlier in life compared to primary OA. Several studies have shown that changes in the mechanical properties of soft tissues in the knee (articulating cartilage and menisci) are associated with worsening OA grades. Changes to the tissue mechanical properties must be considered to generate realistic computational models of individuals who have suffered traumatic injuries to the knee. Therefore, …

Microwave Assisted Heating Of A Ferromagnetically-Doped Propellant For Small Satellites: An Efficacy Study, Thomas Joseph Heffernan

Graduate College Dissertations and Theses

In the interest of mitigating high launch costs, small satellites are often chosen as secondary payloads during launch operations. Their lower mission importance dictates stringent restrictions on the propulsion systems which can be implemented as they cannot contain combustible or toxic agents; a common solution to this prob- lem is implementation of micronozzles with cold-gas propellants in order to generate thrust. The present research explores the efficacy of leveraging microwave-assisted decomposition of a ’green’ chemical blowing agent, namely Azodicarbonamide, as a propellant for use in a microthruster. The thermal evolution of a heterogeneous ferromagnetic-doped propellant is analyzed numerically using COMSOL …

Experimental And Computational Studies Of Heat Transfer In Flexible Two-Dimensional Woven Fiber Ceramic Materials, Rodrigo Penide Fernandez

Graduate College Dissertations and Theses

Flexible thermal protection materials made from two-dimensional woven ceramics fibers are of significant interest for hypersonic inflatable aerodynamic decelerators being developed by NASA for future missions on Mars and other planets. A key component of the thermal shield is a heat-resistant outer ceramic fabric that must withstand harsh aero-thermal atmospheric entry conditions. However, a predictive understanding of heat conduction processes in complex woven-fiber ceramic materials under deformation is currently lacking. This dissertation presents a combined experimental and computational study of thermal conductivity in alumina-based Nextel-440 and silicon carbide Hi-Nicalon 5-harness-satin woven fabrics, using the hot-disk transient plane source method and …

Three-Phase Hybrid Model Of Bacterial Biofilm Growth, Xing Jin

Graduate College Dissertations and Theses

Bacterial biofilms play a critical role in environmental processes, water treatment, human health, and food processing. They exhibit highly complex dynamics due to the interactions between the bacteria and the extracellular polymeric substance (EPS), water, nutrients, and minerals that make up the biofilm. In the current dissertation, a hybrid computational model was proposed for simulation of biofilm growth processes using a multiphase continuum for the transport of water and EPS, as well as nutrient diffusion, and discrete phase particles for simulation of bacterial cells and their interactions. Mass and momentum conservations of each phase and bacterial motion, rotation, growth, division, …

Optimization Of Mixing Efficiency In Low Reynolds Unlike Doublet Injectors By Incorporating Swirl, Samuel Braggins Ligon

Graduate College Dissertations and Theses

One of the largest issues concerning industrial cube satellite manufacturing is the development of propulsion systems at extremely small scales. Bipropellant cube satellite propulsion systems face challenges associated with the mixing of two fluids which operate in low Reynolds number environments. Low Reynolds, or laminar, fluid flow is unique to cube satellite injection systems because of their unprecedented small scale. This work is intended to both test the validity of a proposed cube satellite injection system, and to test the accuracy of numerical method approaches to solving the problem of laminar flow mixing in such devices. The proposed injector is …

Quadrature-Based Gravity Models For The Homogeneous Polyhedron, Jason Pearl

Graduate College Dissertations and Theses

A number of missions to comets and asteroids have been undertaken by major space organizations driving a need to accurately characterize their gravitational fields. This is complicated however by their irregular shapes. To accurately and safely navigate spacecraft in these environments, a simple point-mass gravity model is insufficient and instead higher-fidelity models are required. Several such models exist for this purpose but all posess drawbacks. Moreover, there are some applications for which the currently available models are not particular well suited.

In this dissertation, numerical quadrature and curvilinear meshing techniques are applied to the small body gravity problem. The goal …

Energy Accommodation From Surface Catalyzed Reactions In Air Plasmas, Roland Herrmann-Stanzel

Graduate College Dissertations and Theses

Accurate knowledge of heat transfer to materials in recombining plasmas is needed to improve heat shield designs. A lack of understanding of the chemical component of surface heating motivates the use of conservative assumptions with regards to surface catalysis in the design of thermal protection systems (TPS) that detrimentally impact payload capability. Chemical heating is the release of potential energy from recombining reactive species on the surface to form molecules. For a stable surface interacting with partially-dissociated air, the chemical heating component is due to surface-catalyzed recombination reactions of atomic O and N to produce molecular O2, N2, and NO. …

Design, Prototyping And Fabrication Of Powder Spray Device For Dehydrated Biological Particulates, James Reilly

Graduate College Dissertations and Theses

Tissue sealants of a liquid based formulation are widely studied in biomedical research with many starting to gain FDA approval. To date, little investigation has been put toward methods of application for tissue sealant materials, more specifically a powder based formulation. The focus of this research was to develop and prototype a powder spray device capable of administering powder based formulations with a long-term goal of integrating the device within the clinical setting. Powders can be administered in a variety of dry forms. These forms can range from non-homogenous nanoscale particles to homogeneous micro and nano-scale spheres. Incorporation of therapeutics …

Mechano-Magnetic Telemetry For Urban Infrastructure Monitoring, Daniel Jerome Orfeo

Graduate College Dissertations and Theses

Many cities seek utilities monitoring with centrally managed Internet of Things (IoT) systems. This requires the development of numerous reliable low-cost wireless sensors, such as water temperature and flow meters, that can transmit information from subterranean pipes to surface-mounted receivers. Traditional radio communication systems are either unable to penetrate through multiple feet of earthen and manmade material, or have impractically large energy requirements which necessitate either frequent replacement of batteries, or a complex (and expensive) built-in energy harvesting system. Magnetic signaling systems do not suffer from this drawback: low-frequency electromagnetic waves have been shown to penetrate well through several feet …

Design And Evaluation Of A Tactile Texture Production System, Samuel Benjamin Fertel Shuster

Graduate College Dissertations and Theses

Students who are blind or have low-vision (BLV) do not have the same access to graphical curricular content as their sighted peers. This significantly affects their education, particularly in STEM subjects. Introduction of interactive tactile graphics is one of the only ways for BLV students to access graphical content, and is uniquely suited to teaching drawing skills. The goal of this engineering design project was to expand the capacity of printing technology that produces interactive raised-line graphics by creating a system to print textures that meet specific criteria for usefulness. The addition of textures to tactile graphics is essential for …

Large Eddy Simulation Of Oscillatory Flow Over A Mobile Rippled Bed Using An Euler-Lagrange Approach, Daniel S. Hagan

Graduate College Dissertations and Theses

A volume-filtered Large-Eddy Simulation (LES) of oscillatory flow over a rippled mobile bed is conducted using an Euler-Lagrange approach. As in unsteady marine flows over sedimentary beds, the experimental data, referenced in this work for validation, shows quasi-steady state ripples in the sand bed under oscillatory flow. This work approximately reproduces this configuration with a sinusoidal pressure gradient driven flow and a sinusoidally rippled bed of particles. The LES equations, which are volume-filtered to account for the effect of the particles, are solved on an Eulerian grid, and the particles are tracked in a Lagrangian framework. In the Discrete Particle …

Rotating Magnetometry For Terrestrial And Extraterrestrial Subsurface Explorations, Robert Farrell

Graduate College Dissertations and Theses

Signaling and sensing with rotating magnet sources have both Terrestrial and Extraterrestrial applications. The dual spinning magnet unit presented in this paper is a simple, lightweight solution to help understand soil densities and locate water and ice pockets, for example, on Mars. Traditional magnetic telemetry systems that use energy-inefficient large induction coils and antennas as sources and receivers are not practical for extraterrestrial and remote field sensing applications. The recent proliferation of strong rare-earth permanent magnets and high-sensitivity magnetometers enables alternative magnetic telemetry system concepts with significantly more compact formats and lower energy consumption. There are also terrestrial applications, for …

Novelty Detection Of Machinery Using A Non-Parametric Machine Learning Approach, Enrique Angola

Graduate College Dissertations and Theses

A novelty detection algorithm inspired by human audio pattern recognition is conceptualized and experimentally tested. This anomaly detection technique can be used to monitor the health of a machine or could also be coupled with a current state of the art system to enhance its fault detection capabilities. Time-domain data obtained from a microphone is processed by applying a short-time FFT, which returns time-frequency patterns. Such patterns are fed to a machine learning algorithm, which is designed to detect novel signals and identify windows in the frequency domain where such novelties occur. The algorithm presented in this paper uses one-dimensional …

Numerical Modeling Of Collision And Agglomeration Of Adhesive Particles In Turbulent Flows, Farzad Farajidizaji

Graduate College Dissertations and Theses

Particle motion, clustering and agglomeration play an important role in natural phenomena and industrial processes. In classical computational fluid dynamics (CFD), there are three major methods which can be used to predict the flow field and consequently the behavior of particles in flow-fields: 1) direct numerical simulation (DNS) which is very expensive and time consuming, 2) large eddy simulation (LES) which resolves the large scale but not the small scale fluctuations, and 3) Reynolds-Averaged Navier-Stokes (RANS) which can only predict the mean flow. In order to make LES and RANS usable for studying the behavior of small suspended particles, we …

Wind Turbine Wake Interactions - Characterization Of Unsteady Blade Forces And The Role Of Wake Interactions In Power Variability Control, Daniel Curtis Saunders

Graduate College Dissertations and Theses

Growing concerns about the environmental impact of fossil fuel energy and

improvements in both the cost and performance of wind turbine technologies has spurred

a sharp expansion in wind energy generation. However, both the increasing size of wind

farms and the increased contribution of wind energy to the overall electricity generation

market has created new challenges. As wind farms grow in size and power density, the

aerodynamic wake interactions that occur between neighboring turbines become

increasingly important in characterizing the unsteady turbine loads and power output of

the farm. Turbine wake interactions also impact variability of farm power generation,

acting …

Status Monitoring Of Inflatables By Accurate Shape Sensing, Justin Matthew Bond

Graduate College Dissertations and Theses

The use of inflatable structures in aerospace applications is becoming increasingly widespread. In order to monitor the inflation status and overall health of these inflatables, an accurate means of shape sensing is required. To this end, we investigated two existing methods for measuring simple curvature, or curvature in one-dimension. The first method utilizes a pair of strain sensing Fiber Bragg Gratings (FBGs) separated by a known distance; dividing the difference in strain by the separation distance yields an experimental value for the one-dimensional curvature at a point. The second method makes use of conductive ink-based flex sensors, which give a …

Investigation Of Pyrolysis Gas Chemistry In An Inductively Coupled Plasma Facility, Corey Tillson

Graduate College Dissertations and Theses

The pyrolysis mechanics of Phenolic Impregnated Carbon Ablators (PICA) makes it a valued material for use in thermal protection systems for spacecraft atmospheric re-entry. The present study of the interaction of pyrolysis gases and char with plasma gases in the boundary layer over PICA and its substrate, FiberForm, extends previous work on this topic that has been done in the UVM 30 kW Inductively Coupled Plasma (ICP) Torch Facility. Exposure of these material samples separately to argon, nitrogen, oxygen, air, and carbon dioxide plasmas, and combinations of said test gases provides insight into the evolution of the pyrolysis gases as …

Fabrication And Thermoelectric Characterization Of Stretchable Conductive Latex-Based Composites, Cory Michael Arcovitch

Graduate College Dissertations and Theses

Miniaturized stretchable electronic devices that can be bent and strained elastically without breaking, have drawn considerable research interest in recent years for wearable computers and integrated bio-sensor applications. Portable electrical power harvesting remains a critical challenge in flexible electronics materials. One proposed solution has been to convert waste heat from the human body into electricity using thermoelectric materials. Traditionally, however, these materials are brittle ceramic semiconductors with limited fracture resistance under deformation. The primary objective of this thesis is to address this challenge by fabricating and studying the mechanical, thermal and electrical performance of stretchable composites combining natural latex polymer …

Manufacturing Microfluidic Flow Focusing Devices For Stimuli Responsive Alginate Microsphere Generation And Cell Encapsulation, Michael A. Karasinski

Graduate College Dissertations and Theses

In this paper a novel stimuli responsive hydrogel material, methacrylated sodium alginate beta-cyclodextrin (Alg-MA-β-CD), was used in combination with a microfluidic device to create microspheres. Currently there is no reliable method for fabricating homogeneous stimuli-responsive microspheres, in-house microfluidic devices are not reliable in manufacture quality or long-term use. Alginate hydrogels have many attractive characteristics for bioengineering applications and are commonly used to mimic the features and properties of the extracellular matrix (ECM). Human mesenchymal stem cells (hMSCs) are of top interest to tissue engineers. hMSCs are widely available and can be harvested and cultured directly out of human bone marrow. …

Steady State Simulation Of Pyrolysis Gases In An Inductively Coupled Plasma Facility, Nicholas C. Martin

Graduate College Dissertations and Theses

An important step in the more efficient use of PICA (Phenolic Impregnated Carbon Ablator) as a Thermal Protection System (TPS) material for spacecraft is the understanding of its pyrolysis mechanics. The gases released during pyrolysis and their subsequent interaction with the reactive plasma environment is not yet well understood. The surface recession of PICA as it ablates during testing only makes the study and characterization of the chemical reactions more difficult. To this end, a probe has been designed for this study to simulate, in steady state, the pyrolysis gases within the UVM 30kW Inductively Coupled Plasma (ICP) Torch Facility. …

Assessment Of Surface-Catalyzedreaction Products From Hightemperature Materials In Plasmas, Luke Daniel Allen

Graduate College Dissertations and Theses

Current simulations of atmospheric entry into both Mars and Earth atmospheres for the design of thermal protections systems (TPS) typically invoke conservative assumptions regarding surface-catalyzed recombination and the amount of energy deposited on the surface. The need to invoke such assumptions derives in part from lack of adequate experimental data on gas-surface interactions at trajectory relevant conditions. Addressing this issue, the University of Vermont's Plasma Test and Diagnostics Laboratory has done extensive work to measure atomic specie consumption by measuring the concentration gradient over various material surfaces. This thesis extends this work by attempting to directly diagnose molecular species production …

Structure And Dynamics Of Two Flow Fields Used For Particle Deposition Onto And Removal From A Substrate, Adam Green

Graduate College Dissertations and Theses

A series of experimental studies was performed to investigate two separate fluid impingement flow systems intended for removal of particles from a surface or deposition of particles onto a surface. One of these flow systems is generated using a nozzle that incorporates both tilted jets and suction to create what we call a "bounded vortex flow", consisting of an annular swirling jet and a wall-normal vortex with axial upflow into a suction outlet. The other flow system is generated by a combination of acoustic streaming and substrate heating from an ultrasonic source. The primary methods used in the study for …

Two-Dimensional Numerical Study Of Micronozzle Geometry, Jason M. Pearl

Graduate College Dissertations and Theses

Supersonic micronozzles operate in the unique viscosupersonic flow regime, characterized by large Mach numbers (M>1) and low Reynolds numbers (Re<1000). Past research has primarily focused on the design and analysis of converging-diverging de Laval nozzles; however, plug (i.e. centerbody) designs also have some promising characteristics that might make them amenable to microscale operation. In this study, the effects of plug geometry on plug micronozzle performance are examined for the Reynolds number range Re = 80-640 using 2D Navier-Stokes-based simulations. Nozzle plugs are shortened to reduce viscous losses via three techniques: one - truncation, two - the use of parabolic contours, and three - a geometric process involving scaling. Shortened nozzle are derived from a full length geometry designed for optimal isentropic performance. Expansion ratio (ε = 3.19 and 6.22) and shortened plug length (%L = 10-100%) are varied for the full Reynolds number range. The performance of plug nozzles is then compared to that of linear-walled nozzles for equal pressure ratios, Reynolds numbers, and expansion ratios. Linear-walled nozzle half-angle is optimized to to ensure plug nozzles are compared against the best-case linear-walled design.

Results indicate that the full length plug nozzle delivers poor performance on the microscale, incurring excessive viscous losses. Plug performance is increased by shortening the nozzle plug, with the scaling technique providing the best performance. The benefit derived from reducing plug length depends upon the Reynolds number, with a 1-2% increase for high Reynolds numbers an up to 14% increase at the lowest Reynolds number examined. In comparison to Linear-walled nozzle, plug nozzles deliver superior performance when under-expanded, however, …

Development Of An Additively Manufactured Microthruster For Nanosatellite Applications, Kevin Russell Gagne

Graduate College Dissertations and Theses

Next generation small satellites, also known as nanosatellites, have masses significantly lower than traditional satellites. Including the propellant mass, the total mass of a nanosatellite is often in the range of 1 to 4 $kg$. These satellites are being developed for numerous applications related to research, defense, and industry. Since their popularity began in the early 2000's, limitations on the downscaling of propulsion systems has proven to be problematic. Due to this, the vast majority of nanosatellite missions have limited lifespans of 90-120 days in low Earth orbit before they reenter the Earth's atmosphere. Although satellites on this scale have …

Direct Numerical Simulation Of Ablative Boundaries In Turbulent And Laminar Flows, Ryan Campbell Crocker

Graduate College Dissertations and Theses

Rapid surface ablation by a turbulent flow creates complex flow and surface phenomena arising from the evolving boundary topography and its interaction with a turbulent flow that transports the ablative agent onto the surface. The dynamic nature of ablative flow boundaries generate unsteady flow dynamics and thermodynamics occurring over a wide range of scales. The non-equilibrium nature of these phenomena pose a major challenge to the current fundamental understanding of turbulence, which is mostly derived from equilibrium flows, and to Computational Fluid Dynamics (CFD). The simulation of moving boundaries is a necessary tradeoff between computational speed and accuracy. The most …

Toward An Understanding Of The Breakdown Of Heat Transfer Modeling In Reciprocating Flows, Ian Pond

Graduate College Dissertations and Theses

Reynolds average Navier-Stokes (RANS) modeling has established itself as a critical design tool in many engineering applications, thanks to its superior computational efficiency. The drawbacks of RANS models are well known, but not necessarily well understood: poor prediction of transition, non-equilibrium flows, mixing and heat transfer, to name the ones relevant to our study. In the present study, we use a direct numerical simulation (DNS) of a reciprocating channel flow driven by an oscillating pressure gradient to test several low- and high-Reynolds' RANS models. Temperature is introduced as a passive scalar to study heat transfer modeling. Low-Reynolds' models manage to …

Monitor: Automation Tools For Landscape-Scale Acoustic Monitoring, Jonathan Edward Katz

Graduate College Dissertations and Theses

Climate change coupled with land-use change will likely alter habitats and affect state parameters of the animal populations that dwell in them. Affected parameters are anticipated to include site occupancy and abundance, population range, and phenophase cycles (e.g., arrival dates on breeding grounds for migrant bird species). Detecting these changes will require monitoring many sites for many years, a process that is well suited for an automated system. We developed and tested monitoR, an R package that is designed for long-term, multi-taxa automated passive acoustic monitoring programs. monitoR correctly identified presence for black-throated green warbler and ovenbird in 64% and …

Experimental Investigation And Analysis Of High-Enthalpy Nitrogen Flow Over Graphite, Andrew Lutz

Graduate College Dissertations and Theses

The high-enthalpy flow generated by hypersonic vehicles traveling within the Earth's atmosphere inherently delivers an elevated heat flux to the vehicle surface. In addition to conductive heating, the liberated energy generated by various exothermic chemical reactions occurring at the vehicle surface further augment the total heat load. Quantifying the rates at which these reactions take place is imperative and remains a significant challenge as developers attempt to design the next generation of thermal protection systems.

This study focused on nitrogen recombination and carbon nitridation, as these reactions are ubiquitous to the most aggressive atmospheric re-entry trajectories in which carbon-based ablative …

Effect Of Rainfall Events On The Thermal And Moisture Exposure Of Underground Electric Cables, Andrew Fuhrmann

Graduate College Dissertations and Theses

Cable ampacity analysis is generally performed assuming constant worst-state environmental conditions, which often correspond to a dry soil condition or to a condition with uniform ambient soil moisture content. The characteristic time scale of thermal variation in the soil is large, on the order of several weeks, and is similar to the time scale between rainfall events in many geographic locations. Intermittent rainfall events introduce significant transient fluctuations that influence the thermal conditions and moisture content around a buried cable both by increasing thermal conductivity of the soil and by increasing the moisture exposure of the cable insulation. This paper …

Multi-Satellite Formation Trajectory Design With Topological Constraints Over A Region Of Interest Using Differential Evolution, David William Hinckley

Graduate College Dissertations and Theses

Satellite formation missions allow for scientific measurement opportunities that are only otherwise possible with the use of unrealistically large satellites. This work applies the Evolutionary Algorithm (EA), Differential Evolution (DE), to a 4-satellite mission design that borrows heavily from the mission specifications for Phase 1 of NASA's Magnetospheric Multi-Scale Mission (MMS). This mission specifies goals for formation "quality" and size over the arc when scientific measurements are to be taken known as the Region of Interest (ROI). To apply DE to this problem a novel definition of fitness is developed and tailored to trajectory problems of the parameter scales of …