Engineering Commons^™

Modeling The Influence Of Vibration On Flow Through Embedded Microchannels, Joseph S. Seamons

Theses and Dissertations

The influence of vocal fold (VF) vibration on perfused flow through VF vasculature is an area of research that has previously received limited attention. The aim of the research presented in this thesis was to contribute towards an improved understanding of the effects vibration on perfusion through vasculature within the VFs. This was done using a series of computational simulations of geometric changes to, and perfusion through, microchannels embedded in VF models. A computational structural model based on synthetic VF models used in previous experimental studies was first developed. The model and its embedded microchannel were initially studied under static …

Experiments And Simulations Of Liquid Mass Gauging And Slosh Dynamics In Microgravity, Jedediah Morse Storey

Theses and Dissertations

Advancements in liquid propellant management science and technologies are key to increasing safety, decreasing cost, and increasing payload mass of space missions. Propellant usually comprises a large portion of the total mass of launch vehicles and spacecraft, so liquid propellant sensing, as well as predicting and controlling the motion of it, are important. Electrical Capacitance Tomography (ECT) is an emerging sensing technology that is capable of measuring the distribution of liquid anywhere inside of a tank, potentially making it useful for measuring slosh and gauging mass. An ECT-instrumented tank was successfully tested in microgravity for the first time. Basics of …

Experimental And Numerical Studies On The Projective Dye Visualization Velocimetry In A Squared Vertical Tube, Mark Bradley Johnson

Browse all Theses and Dissertations

In fluid flow experiments, there have been numerous techniques developed over the years to measure velocity. Most popular techniques are non-intrusive such as particle image velocimetry (PIV), but these techniques are not suitable for all applications. For instance, PIV cannot be used in examining in-vivo measurements since the laser is not able to penetrate through the patient, which is why medical applications typically use X-rays. However, the images obtained from X-rays, in particular digital subtraction angiography, are projective images which compress 3D flow features onto a 2D image. Therefore, when intensity techniques, such as optical flow method (OFM), are applied …

Foundations For Finite-State Modelling Of A Two-Dimensional Airfoil That Reverses Direction, Jake Michael Oscar Welsh

McKelvey School of Engineering Theses & Dissertations

Current 3-D finite-state wake models are incapable of simulating a maneuver in which the sign of the free-stream velocity changes direction and the rotor enters its own wake -- as might occur in the case of a helicopter which ascends and then descends. It is the purpose of this work to create a 2-D finite-state wake model which is capable of handling changes in free-stream direction as a precursor to development of a 3-D model that can do the same.

The 2-D finite-state model used for reentry modifications is an existing model created by Peters, Johnson, and Karunamoorthy. By the …

Proper Orthogonal Decomposition Of Reynolds And Dispersive Stresses In Turbulent Boundary Layers Over Multi-Scale Rough Patches, Catherine Virginia Spivey

Dissertations and Theses

Multi-scale rough patches are present in topologies such as urban canopies (cities) and natural landscapes (forests, ocean floors). The flow over such canopies is three-dimensional, with turbulent structures known as secondary flows present in the boundary layer due to the difference in rough surface heterogeneities. Three dimensional instantaneous velocities are analyzed within the roughness sublayer over three generations of multi-scale rough patches at nine vertical planes using particle image velocimetry obtained experimentally. The secondary structures present in the flow are identified in the form of Reynolds and dispersive fluctuations. Proper orthogonal decomposition is employed to characterize the imprint of the …

Improving Quantification Of Mitral Regurgitation Through Computational Fluid Dynamics And Ex Vivo Testing, Alexandra Flowers

Electronic Theses and Dissertations

Mitral regurgitation (MR) is a prominent cardiac disease affecting more than two million people in the United States alone. In order for patients to receive proper therapy, regurgitant volume must first be quantified. As there are an array of methods to do so, the proximal isovelocity surface area (PISA) method continues to be the most accurate and clinically used method. However, there are some difficulties obtaining the necessary measurements need for this when performing transthoracic echocardiography. This study aims to evaluate and present techniques that may be used to more accurately quantify regurgitation through ex vivo testing and computational fluid …

Investigating Ground Interactions Of A Rotocraft Landing Vehicle On Titan, Adam Rozman

Honors Undergraduate Theses

The exploration of celestial bodies has recently advanced from rovers to rotorcraft. This includes the recent flights of Mars Ingenuity and the upcoming Dragonfly mission to explore the terrain of Saturn’s moon Titan as part of NASA’s New Frontiers Program. Flight-based landers can travel quickly to sites kilometers apart and land in complex terrain. Although cruise conditions for these rotorcrafts are well understood, studies are necessary to understand take-off and landing. In ground effect conditions, a rotor wake impinges and reflects off the ground, creating changes in aerodynamics such as increased lift. Additionally, operating over loose surfaces, the rotors can …

Mean Pressure Gradient Effects On Flame-Flow Dynamics In A Cavity Combustor, David M. Smerina

Honors Undergraduate Theses

Pressure gradient confinement effects are experimentally investigated within a cavity combustor to analyze the flame interactions of premixed, cavity stabilized, flames in a high-speed combustor. Pressure gradient confinement effects are generated in a dual mode ramjet-scramjet (DMSR) by varying the wall geometry to form converging, diverging, and nominal configurations. The velocity field and flame position are captured temporally using simultaneous high-speed particle image velocimetry (PIV) and CH chemiluminescence. The evolution of the flow field and flame structure are analyzed, and the high temporal resolution of these measurements allows for the characterization of turbulence-flame interactions. Consideration of the combustion mode and …

Modeling Dewetting, Demixing, And Thermal Effects In Nanoscale Metal Films, Ryan Howard Allaire

Dissertations

Thin film dynamics, particularly on the nanoscale, is a topic of extensive interest. The process by which thin liquids evolve is far from trivial and can lead to dewetting and drop formation. Understanding this process involves not only resolving the fluid mechanical aspects of the problem, but also requires the coupling of other physical processes, including liquid-solid interactions, thermal transport, and dependence of material parameters on temperature and material composition. The focus of this dissertation is on the mathematical modeling and simulation of nanoscale liquid metal films, which are deposited on thermally conductive substrates, liquefied by laser heating, and subsequently …

Electric Field Induced Self-Assembly Of Mesoscale Structured Materials And Smart Fluids, Suchandra Das

Dissertations

This dissertation aims to study the forces that drive self-assembly in binary mixtures of particles suspended in liquids and on fluid-liquid interfaces when they are subjected to a uniform electric or magnetic field. Three fluid-particle systems are investigated experimentally and theoretically : (i) Suspensions of dielectric particles in dielectric liquids; (ii) Suspensions of ferromagnetic and diamagnetic particles in ferrofluids; and (iii) Dielectric particles on dielectric fluid-liquid interfaces. The results of these studies are then used to estimate the parameter values needed to assemble materials with desired mesoscale microstructures.

The first fluid-particle system studied is an electrorheological (ER) fluid formed using …

Analysis Of Fluid Flow In Redox Flow Batteries, Erfan Asadipour

McKelvey School of Engineering Theses & Dissertations

Redox flow batteries (RFB) hold great potential for large-scale stationary energy storage. However, their low energy density compared to other energy storage systems must improve for feasibility. Electrolyte flow distribution affects current density distribution and providing a uniform current density distribution is one way to improve RFB performance. Additionally, reducing the power consumption of the electrolytes’ pump as a source of energy loss in RFB systems increases their efficiency. Investigating both subjects requires analysis of the fluid dynamics in RFB cells.

In this thesis, a novel, computationally cost-effective hydraulic-electrical analogous model (HEAM) was developed to study fluid dynamics by implementing …

Studies Of Two-Phase Flow With Soluble Surfactant, Ryan Peter Atwater

Dissertations

Numerical methods are developed for accurate solution of two-phase flow in the zero Reynolds number limit of Stokes flow, when surfactant is present on a drop interface and in its bulk phase interior. The methods are designed to achieve high accuracy when the bulk Péclet number is large, or equivalently when the bulk phase surfactant has small diffusivity

In the limit of infinite bulk Péclet number the advection-diffusion equation that governs evolution of surfactant concentration in the bulk is singularly perturbed, indicating a separation of spatial scales. A hybrid numerical method based on a leading order asymptotic reduction in this …

Benchmarking Of A Mobile Phone Particle Image Velocimetry System, David Armijo

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

One of the most important tools in a fluid dynamics laboratory is a particle image velocimetry (PIV) system. This system can measure the speed of a fluid flow simply by taking high-speed images of the motion of the fluid, then applying PIV cross-correlation software to calculate speed from the resulting images. The mI-PIV project is in the process of designing a new method of performing PIV by putting the cross-correlation software on a mobile phone application, called mobile Instructional PIV (mI-PIV). This system is an innovative stepping stone in making PIV systems more widely available. It is designed to be …

Fluted Films Caused By Gravity Driven Water Drainage From Vertical Tubes, Matthew B. Jones

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

When a stationary mass of water in a vertical tube is suddenly released, it creates a variety of artistic shapes and behaviors as it escapes the tube exit. As the descending water accelerates in the tube, friction along the tube wall slows the outer radius, resulting in a moving film entrained on the tube that trails the main body of water. When this film exits the tube, surface tension, gravity, and inertia interact to cause the film to create a wide variety of shapes, including jets, tubes, water bells, champagne glasses, and bubbles; rich forms that appear in other natural …

Delaying Flow Separation Using Piezoelectric Actuators, Kenechukwu Okoye

Honors Theses

Flow separation causes aircraft to experience an increase in drag degrading their aviation performance. The goal of the study was to delay flow separation on an airfoil by embedding a high-frequency translational piezoelectric actuator along the surface of the airfoil. This study investigated the extent to which the high-frequency translational piezoelectric actuator displaces the flow separation downstream or prevents it altogether utilizing a fog-based flow visualization experiment. The actuators with two actuation surfaces were embedded on the suction surface of an Eppler 862 airfoil model and placed in a low-speed wind tunnel. Dry ice fog streams were injected into the …

Characterization Of Single- And Multi-Phase Shock-Accelerated Flows, Patrick John Wayne

Mechanical Engineering ETDs

Experiments conducted in the Shock Tube Facility at the University of New Mexico are focused on characterization of shock-accelerated flows. Single-phase (gaseous) initial conditions consist of a heavy gas column of sulfur hexafluoride seeded with approximately 11% acetone gas by mass. Visualization of the image plane for gaseous initial conditions is accomplished via planar laser-induced fluorescence (PLIF) with a high-powered Nd:YAG ultraviolet laser and an Apogee Alta U-42 monochrome CCD camera, with a quantum efficiency > 90%. Multi-phase (gas-solid) initial conditions consist of glass micro-beads deposited on small 1-cm diameter discs of specific surface chemistry, mounted flush with the bottom wall …

A Study Of Several Applications Of Parallel Computing In The Sciences Using Petsc, Nicholas Stegmeier

Electronic Theses and Dissertations

The importance of computing in the natural sciences continues to grow as scientists strive to analyze complex phenomena. The dynamics of turbulence, astrophysics simulations, and climate change are just a few examples where computing is critical. These problems are computationally intractable on all computing platforms except supercomputers, necessitating the continued development of efficient algorithms and methodologies in parallel computing. This thesis investigates the use of parallel computing and mathematical modeling in the natural sciences through several applications, namely computational fluid dynamics for impinging jets in mechanical engineering, simulation of biofilms in an aqueous environment in mathematical biology, and the solution …

Investigating The Effect Of An Upstream Spheroid On Tandem Hydrofoils, Joel Tynan Guerra

Master's Theses

This thesis documents a series of three dimensional unsteady Reynolds Averaged Navier-Stokes CFD simulations used to investigate the influence of an upstream prolate spheroid body on tandem pitching hydrofoils. The model is validated by performing separate CFD simulations on the body and pitching hydrofoils and comparing results to existing experimental data. The simulations were run for a range of Strouhal numbers (0.2-0.5) and phase differences (0-π). Results were compared to identical simulations without an upstream body to determine how the body affects thrust generation and the unsteady flow field.

The combined time-averaged thrust increases with Strouhal number, and is highest …

Investigations Into The Airside Cooling Of A Heat Exchanger, David Vallet

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this study we investigate the air-side cooling of a flat-plate fin and tube heat transfer condenser with numerical simulations. A new design is proposed which utilises vortex generators to direct the flow in such a way as to remove some of the stagnant heated air that collects in the wake of the pipes. A comparative study of the proposed design and a standard tube and fin condenser is conducted by varying the air side entrance velocities. The Shear Stress Tension, SST $\kappa - \omega$ 2-equation turbulent model is used to solve the RANS model in ANSYS Fluent 18. The …

Electro-Drop Bouncing In Low-Gravity, Erin Stivers Schmidt

Dissertations and Theses

We investigate the dynamics of spontaneous jumps of water drops from electrically charged superhydrophobic dielectric substrates during a sudden step reduction in gravity level. In the brief free-fall environment of a drop tower, with a non-homogeneous external electric field arising due to dielectric surface charges (with surface potentials 0.4-1.8 kV), body forces acting on the jumped drops are primarily supplied by polarization stress and Coulombic attraction instead of gravity. This electric body force leads to a drop bouncing behavior similar to well-known phenomena in 1-g₀, though occurring for much larger drops (~0.5 mL). We show a simple …

Detection Method Of Subclinical Atherosclerosis Of The Carotid Artery With A Hemodynamics Modeling Approach, Marisa Peressini

Master's Theses

Subclinical atherosclerosis is an important area of research to evaluate stroke risk and predict localization of plaque. The current methods for detecting atherosclerosis risk are insufficient because it is based on The Framingham Risk Score and carotid intima media thickness, therefore an engineering detection model based on quantifiable data is needed. Laminar and turbulent flow, dictated by Reynolds number and relative roughness, was modeled through the carotid artery bifurcation to compare shear stress and shear rate. Computer-aided design and fluid flow software were used to model hemodynamics through the carotid artery. Data from the model was derived from governing equations …

Mechanisms And Identification Of Unsteady Separation Development And Remediation, Matthew Scott Melius

Dissertations and Theses

Unsteady flow separation represents a highly complex and important area of study within fluid mechanics. The extent of separation and specific time scales over which it occurs are not fully understood and has significant consequences in numerous industrial applications such as helicopters, jet engines, hydroelectric turbines and wind turbines. A direct consequence of unsteady separation is the erratic movement of the separation point which causes highly dynamic and unpredictable loads on an airfoil. Current computational models underestimate the aerodynamic loads due to the inaccurate prediction of the emergence and severity of unsteady flow separation especially in response to a sudden …

Extraction And Localization Of Noise-Related Flow Structures In High Speed Jets, Pinqing Kan

Dissertations - ALL

The jet noise problem, or the noise radiation from high-speed flow interactions, still remains unresolved after over sixty years of research. With the growing aviation industry, more communities are exposed to noise pollution from aircrafts; and better control strategies are needed to meet the more stringent noise regulations.

This thesis analyzes two sets of high-speed jet flow data and aims at better understanding the flow dynamics and noise radiation mechanism. The first set of data consists of subsonic / transonic axisymmetric jets and the second dataset is of a more advanced configuration: a two-stream supersonic rectangular jet with a flat …

Cold Gas Dynamic Spray – Characterization Of Polymeric Deposition, Trenton Bush

Masters Theses

When a solid, ductile particle impacts a substrate at sufficient velocity, the resulting heat, pressure, and plastic deformation can produce bonding at the interface. The use of a supersonic gas flow to accelerate such particles is known as Cold Spray deposition. The Cold Spray process has been commercialized for some metallic materials, but further research is required to unlock the exciting material properties possible with polymeric compounds. In this work, a combined computational and experimental study a) simulated and optimized the nozzle flow conditions necessary to produce bonding in a polyethylene particle, b) developed and fabricated an experimental device, and …

Solution Of Fully-Coupled Shallow Water Equations And Contaminant Transport Using A Primitive Variable Riemann Solver And A Semi-Discrete Supg Method, Faranak Behzadi

Masters Theses and Doctoral Dissertations

In the present dissertation, a finite volume and a finite element model are developed and tuned for the solution of the fully-coupled two-dimensional Shallow Water and Contaminant transport Equations with arbitrary bed topography and wetting-drying fronts. A Riemann-solver finite volume scheme, using primitive variables rather than conserved variables, and a semi-discrete Streamline Upwind Petrov-Galerkin (SUPG) method in finite element context are applied to compare the performance of these two numerical models. The Riemann-solver scheme is based on the unstructured finite volume discretization using primitive-variable Roe-flux approximation with an entropy fix. Second-order accuracy in space and time, an implicit scheme based …

Large Length Scale Capillary Fluidics: From Jumping Bubbles To Drinking In Space, Andrew Paul Wollman

Dissertations and Theses

In orbit, finding the "bottom" of your coffee cup is a non-trivial task. Subtle forces often masked by gravity influence the containment and transport of fluids aboard spacecraft, often in surprising non-intuitive ways. Terrestrial experience with capillary forces is typically relegated to the micro-scale, but engineering community exposure to large length scale capillary fluidics critical to spacecraft fluid management design is low indeed. Low-cost drop towers and fast-to-flight International Space Station (ISS) experiments are increasing designer exposure to this fresh field of study. This work first provides a wide variety of drop tower tests that demonstrate fundamental and applied capillary …

Modeling Shock Waves Using Exponential Interpolation Functions With The Least-Squares Finite Element Method, Bradford Scott Smith Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

The hypothesis of this research is that exponential interpolation functions will approximate fluid properties at shock waves with less error than polynomial interpolation functions. Exponential interpolation functions are derived for the purpose of modeling sharp gradients. General equations for conservation of mass, momentum, and energy for an inviscid flow of a perfect gas are converted to finite element equations using the least-squares method. Boundary conditions and a mesh adaptation scheme are also presented. An oblique shock reflection problem is used as a benchmark to determine whether or not exponential interpolation provides any advantages over Lagrange polynomial interpolation. Using exponential interpolation …

Developing And Testing An Anguilliform Robot Swimming With Theoretically High Hydrodynamic Efficiency, John B. Potts Iii

University of New Orleans Theses and Dissertations

An anguilliform swimming robot replicating an idealized motion is a complex marine vehicle necessitating both a theoretical and experimental analysis to completely understand its propulsion characteristics. The ideal anguilliform motion within is theorized to produce ``wakeless'' swimming (Vorus, 2011), a reactive swimming technique that produces thrust by accelerations of the added mass in the vicinity of the body. The net circulation for the unsteady motion is theorized to be eliminated.

The robot was designed to replicate the desired, theoretical motion by applying control theory methods. Independent joint control was used due to hardware limitations. The fluid velocity vectors in the …

Dosi In Novel Geometry Dishes, Jonathan Lawrence Lambert Jones

Electronic Theses and Dissertations

Effects of hemodynamic forces on cellular response are well studied. Wall shear stress is regularly accepted as the primary hemodynamic force affecting cellular response. Hemodynamic forces studies utilize Petri dishes on orbital shakers to grow cells for the experiments since this is an easily scalable system. However, characterizing the hemodynamics is difficult since the oscillatory swirling motion creates multidirectional and variable magnitude shear throughout the dish. Thus, a novel geometry dish that could create uniaxial shear with less variation in magnitude would be advantageous for studying shear stress effects on cellular response. The purpose of this thesis was to explore …

Computational Fluid Dynamics Validation Of Buoyant Turbulent Flow Heat Transfer, Jared M. Iverson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Computational fluid dynamics (CFD) is commonly used to visualize and understand complicated fluid flow and heat transfer in many industries. It is imperative to validate the CFD computer models in order to avoid costly design choices where experimentation cannot be used to ratify the predictions of computer models. Assessments of CFD computer models in the literature conclude that significant errors occur in computer model predictions of fluid flow influenced by buoyancy forces.

The Experimental Fluid Dynamics Laboratory at Utah State University constructed a wind tunnel with which to perform experiments on buoyancy induced fluid flow. The experiments measured the heat …