Engineering Commons^™

Analysis Of An Electrospray Thruster With A Concave Propellant Meniscus, Adam Nicholas Huller

Masters Theses

The low thrust, high specific impulse, and low mass of electrospray thrusters (ETs) make them ideal for maneuvering nanosatellites, especially with the new requirement to deorbit a satellite within five years of completing its mission. These innovative thrusters use electrohydrodynamic principles of electrospray (ES) to provide thrust. These principles have been subject to much research over the past decade, though much more research is needed to fully understand the underlying physics of these thrusters. The first part of this study establishes a procedure for analyzing the theoretical thrust performance of an ET, by using propellant properties and well-documented ES scaling …

Boundary Layer Measurements On The Bolt Ii Geometry Using Pressure And Temperature Sensitive Paints, Jacob Gaetano Butera

Masters Theses

Hypersonic vehicles are subjected to an extreme aerothermodynamic environment dominated by intense thermal loading which is amplified further when the local boundary layer state transitions from a laminar to a turbulent state. Due to weight and complexity considerations, it is not feasible to incorporate thermal protection systems (TPS) over an entire hypersonic body. Therefore, it is critically important to identify and predict where the boundary layer will undergo transition such that the thermal protection system can be focused on the most at-risk areas. This work attempts to observe boundary layer transition on the Boundary Layer Transition (BOLT) II flight test …

A Computational Analysis Of Hypersonic Store Separations, Ryan C. Savery

Masters Theses

Many current hypersonic vehicles involve shrouds, fairings, boosters, or ejectable payloads separating during flight. It is imperative that they do not strike each other after separation as this typically results in damage or loss of vehicle. This requires a detailed understanding of the flow features involved such as shock waves, expansion waves, shock reflections, and shock wave boundary layer interactions influencing the vehicles' attitude and trajectory. Experimental and flight tests of these scenarios are costly and need massive infrastructure which require difficult measurement techniques to characterize the flow field. Alternatively, numerical simulations can provide accurate, low-cost, and efficient predictions of …

Flow Control Over An Airfoil Using Synthetic Jet, Satyam Anil Mistry

Masters Theses

In this study, the unsteady, turbulent flow over NACA 0015 was analyzed using synthetic jets. The study focused on applying the numerical method using the commercial CFD solver Ansys Fluent. The synthetic jet simulation was carried out for Re = 896,000 for two angles of attack: 10 and 14 degrees. The optimal jet amplitude and jet frequency were determined from a range of amplitudes of 2.0 to 4.0 and frequencies of 0.4 Hz to 1.2 Hz while the jet location, jet angle, and jet width were fixed. The results showed that for both angles, the optimal amplitude and frequency were …

Enabling Premixed Hydrogen-Air Combustion For Aeroengines Via Laboratory Experiment Modeling, Christopher James Caulfield

Masters Theses

All combustion systems from large scale power plants to the engines of cars to gas turbines in aircraft are looking for new fuel sources. Recently, clean energy for aviation has come into the foreground as an important issue due to the environment impacts of current combustion methods and fuels used. The aircraft industry is looking towards hydrogen as a new, powerful, and clean fuel of the future. However there are several engineering and scientific challenges to overcome before hydrogen can be deployed into the industry. These issues
range from storing the hydrogen in a viable cryogenic form for an aircraft …

An Experimental Investigation Of The Effect Of Narrowband Freestream Noise On Fundamental Transitional Shockwave-Boundary Layer Interaction Mechanisms, Zane Matthew Shoppell

Masters Theses

Recent work at the University of Tennessee Space Institute has demonstrated that the resonant behavior observed in the spectra of cylinder- and blunt-fin-generated XSBLIs is connected to fundamental fluid mechanisms within the boundary layer. Therefore, a test campaign was conducted to characterize the fundamental mechanisms that drive the low-frequency unsteadiness in cylinder- and blunt-fin-generated shockwave-boundary layer interactions, specifically shockwave-boundary layer interactions in which the incoming boundary layer is undergoing a laminar-to-turbulent transition. This research aims to develop a deeper understanding of such interactions and characterize the resonant behavior observed in past work by varying the sweepback angle of a hemicylindrical …

Exploring The Structure And Dynamics Of Shock/Turbulent Boundary Layer Interactions Generated By Swept Compression Ramps In A Mach 2 Freestream, Daniel S. Allen

Masters Theses

This thesis reports the investigation of the unsteadiness of a 2D and 3D swept shock-wave/turbulent boundary layer interaction (STBLI) and the effect the extent of subsonic flow has on the separation location. Two swept compression ramp cases are investigated at Mach 2 freestream conditions – a high sweep of 30 degrees and a low sweep of 10 degrees both having the same compression angle of 22.5 degrees in the vertical plane. Using a number of diagnostic techniques including stereoscopic and planar particle image velocimetry (PIV) and unsteady pressure sensitive paint (PSP) anchored with pressure transducers, the unsteadiness, the extent of …

Upscaling And Development Of Linear Array Focused Laser Differential Interferometry For Simultaneous 1d Velocimetry And Spectral Profiling In High-Speed Flows, Kirk Davenport

Masters Theses

In this research a new configuration of linear array-focused laser differential interferometry (LA-FLDI) is described. This measurement expands on previous implementations of LA-FLDI through the use of an additional Wollaston prism. This additional prism expands the typical single LA-FLDI column into two columns of FLDI point pairs. The additional column of probed locations allows for increased spatial sampling of frequency spectra as well as the addition of simultaneous wall normal velocimetry measurements. The new configuration is used to measure the velocity profile and frequency content across a Mach 2 turbulent boundary layer at six wall normal locations simultaneously. Features of …

Analysis Of Turbulent Flow Behavior In Helicopter Rotor Hub Wakes, Forrest Mobley

Masters Theses

The rotor hub is one of the most important features of all helicopters, as it provides the pilot a means for controlling the vehicle by changing the characteristics of the main and tail rotors. The hub also provides a structural foundation for the rotors and allows for the rotor blades to respond to aerodynamic forces while maintaining controllability and stability. Due to the inherent geometry and high rate of rotation, the rotor hub in its current form acts a large bluff body and is the primary source of parasite drag on the helicopter, despite its relatively small size. The rotor …

Temperature Sensitive Paint Investigation Of A Cylinder Induced Shockwave Boundary Layer Interaction, Caleb Bell

Masters Theses

A urethane based temperature sensitive paint was employed to measure the surface temperature characteristics of both a cylinder perpendicular to a Mach 2.3 flow and the floor of the tunnel with varying gaps between the base of the cylinder and the tunnel floor. The first goal of this study was to determine the effectiveness of a temperature sensitive paint at providing quantitative and qualitative temperature data on supersonic flow interactions in a standard supersonic blow down wind tunnel. The second goal was to determine the heat transfer and surface temperature of the cylinder and the areas of the tunnel wall …

Optical Measurements Of Viscous Interactions On A Hollow-Cylinder / Flare In A Mach 4 Freestream, Jack William Cobourn

Masters Theses

Despite decades of research, shock-wave/boundary-layer interactions and laminar-turbulent transition remain uncertainties in the design of hypersonic vehicles. Due to the significant demand for hypersonic capabilities and the relevance of these flow physics to air-breathing, high-lift, hypersonic vehicles, continued study is necessary. In order to support such study at the University of Tennessee Space Institute, two optical diagnostics were investigated for use in the Mach 4 Ludwig tube at the Tennessee Aerothermal Laboratory, focused laser differential interferometry and schlieren. Significant attention was given to the theory behind and application of focused laser differential interferometry to support future work at the University …

Investigation Of Predicted Helicopter Rotorhub Drag And Wake Flow With Reduced Order Modeling, Tristan David Wall

Masters Theses

The rotor hub is one of the most important components of the modern helicopter. This complex collection of linkages and plates has numerous responsibilities, including the translation of pilot input to system response, anchoring the blades to the rotor mast, and sustaining the various forces transmitted by the blades. Due its intricate design and relatively small sized components the rotor hub interacts with the incoming flow to create a highly chaotic, turbulent wake which impinges on the fuselage and empennage. This assembly has also been found to be one of the primary contributors to the total vehicle parasite drag. Unfortunately …

An Experimental Investigation Of High-Speed Air-Breathing Vehicle Performance Metrics, Katherine M. Stamper

Masters Theses

High-speed air-breathing vehicles are one of the main hypersonic vehicles currently being developed. There is a current push by major world powers to develop these vehicles and one of the major limiting factors is engine design. The high-speed air-breathing vehicles necessitate an engine that can perform at higher speeds and higher temperatures, such as a scramjet. This engine is broken into three main parts: the inlet, isolator, and combustor. One of the primary concerns for these vehicles is engine unstart, which is when there is no longer supersonic flow through the engine and the engine can no longer perform. This …

Numerical Investigation Of Leading-Edge Modifications Of A Naca Airfoil, Anisur Rahman Ikram

Masters Theses

A parametric investigation was carried out to understand the flow characteristics of tubercle airfoils and to determine the best approach and parameters for designing a tubercle airfoil. For this purpose, a straight edge base airfoil (NACA 4414) and several tubercle airfoils, by modifying the leading edge of the base airfoil, were created in SolidWorks and tested with Computational Fluid Dynamics (CFD) application software Star CCM+.

Alternative tubercle airfoil with elliptical bumps demonstrated superior post-stall performance when compared to their straight edge counterparts; their post-stall lift did not decrease drastically. However, their pre-stall lift coefficients were always lower than the base …

Comparison Of Reynolds-Averaged Navier-Stokes Turbulence Models For Simulating Boundary Layers In Hypersonic Flows, Jorge-Valentino Kurose Bretzke

Masters Theses

“This study describes the use of Computational Fluid Dynamics (CFD) codes to simulate hypersonic boundary layers using several different turbulent closure models and comparing Reynolds-Averaged Navier-Stokes (RANS) simulations against Direct Numerical Simulations (DNS) of similar test cases. The test cases in this study consist of a flat plate in a Mach 8 freestream with a zero pressure gradient and wall recovery ratio of 0.48, as well as a Mach 8 axisymmetric nozzle also with a cold wall. The RANS models used in this study are the Spalart-Allmaras model, Baldwin-Lomax model, Menter K-Omega Baseline and Menter K-Omega Shear Stress Transport models. …

Development Of A Multi-Jointed Wing Surface Mover, Collin Arthur Strassburger

Masters Theses

The field of ornithopter research has reached a point where it has become commonplace for Computational Fluid Dynamics (CFD) solvers to have built-in capabilities for rigid solid body motion. This is suitable for micro air vehicles (MAVs) yet is often not exible enough to model wings with dynamic internal structure, such as the wings of birds and bats. There is currently no program available to perform the surface motion of a wing which has multiple independently moving joints. The code, detailed in this paper, provides the user with this type of capability. The bone lengths, joint angle properties, and thickening …

Improving The Efficiency Of Wind Farm Turbines Using External Airfoils, Shujaut Bader

Masters Theses

Wind turbine efficiency typically focuses on the shape, orientation, or stiffness of the turbine blades. In this thesis, the focus is instead on using static fixed airfoils in proximity to the wind turbine to control the airflow coming out of the turbine. These control devices have three beneficial effects. (1) They gather air from “higher up” where the air is moving faster on average (and therefore has more kinetic energy in it). (2) They throw the used (and slowed down air) downwards. This means that any turbines in the wind farm behind the lead turbines do not get “stale” air. …

A Numerical Study Of The Limiting Cases Of Cylinder-Induced Shock Wave/Boundary Layer Interactions, Stefen Albert Lindorfer

Masters Theses

One of the limiting factors in the design of supersonic and hypersonic vehicles remains the prediction and control of the high aerodynamic, thermodynamic, acoustic, and structural loads generated by a shock wave/boundary layer interaction (SWBLI or SBLI). In conjunction with an experimental campaign produced within the research group, a numerical study was performed using a semi-infinite cylinder to generate a SWBLI at Mach 1.88 with both laminar and turbulent boundary layers. The goals were not only to better understand the complex flow surrounding the cylinder-induced turbulent interaction, but also to establish the interaction bounds of the limiting cases of a …

Angle Of Attack Determination Using Inertial Navigation System Data From Flight Tests, Jack Kevin Ly

Masters Theses

Engineers and pilots rely on mechanical flow angle vanes on air data probes to determine the angle of attack of the aircraft in flight. These probes, however, are costly, come with inherent measurement errors, affect the flight characteristics of the aircraft, and are potentially dangerous in envelope expansion flights. Advances in the accuracy, usability, and affordability of inertial navigation systems allow for angle of attack to be determined accurately without direct measurement of the airflow around the aircraft. Utilizing an algorithm developed from aircraft equations of motion, a post-flight data review is completed as the first step in proving the …

Development, Analysis, And Optimization Of A Swirl-Promoting Mean Flow Solution For Solid Rocket Motors, Andrew Steven Fist

Masters Theses

This work demonstrates and analyses a new flow candidate for describing the internal gaseous motion in simulated rocket motors. The fundamental features of this solution include the conservation of key system properties also incorporated in the classic Taylor-Culick (TC) system (i.e. inviscid, axisymmetric, steady and rotational properties), while allowing for the development of a swirling velocity component. The work compares the new solution to the development and formulation of the classic TC system, ultimately identifying that both the new and classic solutions are special cases of the Bragg-Hawthorne equation. Following this development, the text then explores the development of energy-optimized …

The Design And Computational Validation Of A Mach 3 Wind Tunnel Nozzle Contour, Sarah Elizabeth Adams

Masters Theses

The objective of this effort was to design and validate a Mach 3 wind tunnel nozzle contour. The nozzle will be used for an existing facility, replacing a Mach 2.3 nozzle. The nozzle contour was design using the widely-distributed CONTUR code developed by Sivells. The program uses a combination of analytical solutions and the method of characteristics in order to calculate a nozzle contour. A nozzle contour adhering to the existing geometry requirements was achieved through an iterative process. The flowfield of the finalized nozzle contour was solved using ANSYS fluent. The solution results were analyzed for flow uniformity.

Dji S-1000 Spreading Wings Octocopter: Determination Of Rotor Downwash Slipstream Size, Jonathan Lemieux

Masters Theses

The DJI S-1000 Spreading Wings octocopter rotor downwash slipstream area of influence was measured in axial climb conditions and in straight level flight. These data were gathered using a simple apparatus of distributed anemometers and a custom made boom affixed to the drone. Straight level flight tests incurred autopilot oscillations that rendered the data gathering and analysis challenging. The best quality data was acquired during the axial climb flight tests. The axial climbs were conducted in calm winds. It was determined that the axial climbs under these conditions displaced the rotor slipstream 9 ± 2.5 cm to the rear of …

A Computational Evaluation Of Transonic Wind Tunnel Wall Interference On High Aspect Ratio Models In The Arnold Engineering Development Complex 16 Foot Transonic Tunnel, William Calain Schuman

Masters Theses

One of the inherent difficulties in utilizing a ventilated test section wind tunnel is the interaction of the model flow field and the test section walls. If high quality aerodynamic data is required for the system under test it is necessary to determine the impact of the test section walls on the flow field around the model. A parametric study was undertaken using the CFD code USM3Dns to determine the impact of model size and wingspan on observed transonic wind tunnel wall interference. The study used a simplified model of the Propulsion Wind Tunnel 16T test section as the test …

Improved Modeling Of Atmospheric Entry For Meteors With Nose Radii Between 5cm And 10m, Jakob Dale Brisby

Masters Theses

Atmospheric entry studies typically look closely at the peak heating rate that a body encounters during its trajectory. This is an extremely important phenomenon to study because it allows engineers to determine if a trajectory is possible with given materials and craft design specifications. It also allows designers to choose what type of method will be used for mitigating the enormous heat fluxes during entry. In general, it is accepted that during the super-sonic flight regime the body will continue to be heated and an ablative heat shield often is used to deal with these heating processes. The theory outlined …

Characterization Of Convective Heat Transfer Coefficients Of A Self-Aspirated Hot Gas Temperature Probe, Samuel David Stephens

Masters Theses

The objective of this work is to provide a Nusselt Number in a Reynolds Number and Prandtl Number correlation for various surfaces of an aspirated total temperature probe exposed to high temperature flow. The experiment discharged thermally stabilized dry air through large scale models of the probe surfaces in a blow-down wind tunnel and a direct connect facility. The model contained electrically heated sections exposed to the flow which were thermally insulated and instrumented with thermocouples. Experimental data were recorded for several Reynolds numbers and heater positions across three configurations. Uncertainty analysis was performed by the Monte Carlo uncertainty propagation …

Analysis Of Flammability Limits And Gas Properties Of A Solid Rocket Motor Test In A High Altitude Test Facility, Richard Scott Kirkpatrick

Masters Theses

The testing of solid and liquid rocket propulsion systems in a confined test facility often produces explosive or flammable gases which must be safely handled. Often inert gases such as nitrogen are used to lower the molar fraction of oxygen to low enough levels to minimize the probability of an explosion or deflagration. For this thesis, the chemical composition of these rocket exhaust gases mixed with air were used to determine the flammability limits of the gas mixture. Using the ideal gas law and the conservation of mass, the exhaust gas composition and gas properties such as pressure, temperature, volume …

Cfd Analysis Of Viscosity Effects On Turbine Flow Meter Performance And Calibration, Carl Tegtmeier

Masters Theses

In this research turbine flow meters were studied, using computational fluid dynamics (CFD) modeling to the study effects of viscosity on the flow meters, across a wide range of operation, to improve our understanding and their performance. A three-dimensional computational model was created for a typical flow meter geometry. The work began with a steady state model to provide an acceptable initial condition for further simulations. These results were input into a transient model that has a rotating zone around the rotor to provide insight into the interaction between static and rotational structures. In order to automatically adjust the rotor …

Modeling Dynamic Stall For A Free Vortex Wake Model Of A Floating Offshore Wind Turbine, Evan M. Gaertner

Masters Theses

Floating offshore wind turbines in deep waters offer significant advantages to onshore and near-shore wind turbines. However, due to the motion of floating platforms in response to wind and wave loading, the aerodynamics are substantially more complex. Traditional aerodynamic models and design codes do not adequately account for the floating platform dynamics to assess its effect on turbine loads and performance. Turbines must therefore be over designed due to loading uncertainty and are not fully optimized for their operating conditions. Previous research at the University of Massachusetts, Amherst developed the Wake Induced Dynamics Simulator, or WInDS, a free vortex wake …

New Generator Control Algorithms For Smart-Bladed Wind Turbines To Improve Power Capture In Below Rated Conditions, Bryce B. Aquino

Masters Theses

With wind turbines growing in size, operation and maintenance has become a more important area of research with the goal of making wind energy more profitable. Wind turbine blades are subjected to intense fluctuating loads that can cause significant damage over time. The need for advanced methods of alleviating blade loads to extend the lifespan of wind turbines has become more important as worldwide initiatives have called for a push in renewable energy. An area of research whose goal is to reduce the fatigue damage is smart rotor control. Smart bladed wind turbines have the ability to sense aerodynamic loads …

Turbulent Transition In Electromagnetically Levitated Liquid Metal Droplets, Jie Zhao

Masters Theses

The condition of fluid flow has been proven to have a significant influence on a wide variety of material processes. In electromagnetic levitation (EML) experiments, the internal flow is driven primarily by electromagnetic forces. In 1-g, the positioning forces are very strong and the internal flows are turbulent. To reduce the flows driven by the levitation field, experiments may be performed in reduced gravity and parabolic flights experiments have been adopted as the support in advance. Tracer particles on the surface of levitated droplets in EML experiment performed by SUPOS have been used to investigate the transition from laminar to …