Aerodynamics and Fluid Mechanics Commons^™

Effect Of Morphology And An Upstream Tall Building On A Street Canyon Flow, Haoran Du

Electronic Thesis and Dissertation Repository

The effects of the morphological model and the existence of an upstream tall building on the turbulent street canyon flow and the overlying boundary layer are investigated in a wind tunnel, using Stereoscopic Particle Image Velocimetry (S-PIV) measurements. The velocity variances, Reynolds shear stress, and turbulent kinetic energy are found to be larger than in a similar idealized street canyon model. Increasing building height results in a decrease in vertical mass fluxes across the opening of the canyon, at least in the canyon portion directly downstream of the building. The interaction between the large-scale structures in the overlying boundary layer …

Computational Analysis Of Steady Hypersonic Flow Fields Of Nasa Benchmark Geometries Utilizing Ansys Fluent, Aidan Murphy

McKelvey School of Engineering Theses & Dissertations

The Hypersonic International Flight Research Experimentation (HIFiRE) program explores and advances hypersonic aerospace systems by developing a multitude of test flight geometries and conducting experimental test flights to obtain data for use in validation of computational models and results. This study focuses on computational validation of heat flux, and calculation of static pressure profiles, skin friction coefficient profiles, and flow contours. The flow fields studied are for Mach number 7.18 and angles of attack (α) of 0° & 2°. These flow fields include many compressible flow features such as an expansion wave at the intersection of the cone and flat …

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 …

Investigation Of Dynamic Hybrid Rans-Les Turbulence Modeling For Cfd Simulation Of A Normal Jet In Crossflow, Cole Simmonds

Mechanical Engineering Undergraduate Honors Theses

The jet in crossflow is a canonical flow feature in many natural and engineered systems, ranging from pollutant dispersal in exhaust discharge to film cooling of high-temperature components in modern propulsion systems. The ability to computationally predict the flow features of jets in crossflow accurately and efficiently is therefore important for analysis and design for a wide variety of applications. In this study the capabilities of the dynamic hybrid RANS-LES (DHRL) turbulence modeling technique are investigated and compared to an industry standard Reynolds-averaged Navier-Stokes model (k-omega SST) in order to quantify the accuracy and computational cost of the two approaches. …

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 …

Flow Characterization Over Biomimetic Fish Scale Arrays, Isaac Nr Clapp Mr.

Electronic Thesis and Dissertation Repository

The contributions of drag to energy consumption in the transportation sector are significant and often unavoidable. Biomimetic surfaces are promising as passive drag reduction mechanisms. Among them, fish scale arrays are beneficial in the laminar and transitional flow regimes but lack fundamental understanding. This research addressed this need and investigated the underlying flow mechanisms over fish scale arrays. Experimental measurements revealed the presence of flow recirculation, streamwise velocity streaks, spanwise velocity fluctuations, and wall normal vorticity streaks, all of which play a role in the near wall flow behaviour. Numerical simulations revealed the superior friction drag reduction capabilities of the …

Superfly Amphibian, Devonte Andrews, Ahmed Hamza, Kwesi Onumah, Eva Sanchez

Senior Design Project For Engineers

Following a Short Takeoff and Landing (STOL) mission profile, this seaplane is designed to carry 19 passengers and 1 flight crew with a range of 200 nautical miles. The seaplane is equipped with two turbo-prop engines and is economically comparable to current seaplanes in terms of servicing and operating expenses. The aircraft is capable of operating in remote locations with limited infrastructure due to its STOL abilities, allowing for increased access to difficult-to-reach areas. The seaplane's design incorporates modern materials and technologies to enhance efficiency, safety, and comfort for passengers and crew. The aircraft's versatility and cost-effectiveness make it an …

A Simulation Of The Impacts Of Climate Change On Civil Aircraft Takeoff Performance, Thomas D. Pellegrin

Doctoral Dissertations and Master's Theses

Climate change affects the near-surface environmental conditions that prevail at airports worldwide. Among these, air density and headwind speed are major determinants of takeoff performance, and their sensitivity to global warming carries potential operational and economic implications for the commercial air transport industry. Previous archival and prospective research observed a weakening in headwind strength and predicted an increase in near-surface temperatures, respectively, resulting in an increase in takeoff distances and weight restrictions. The main purpose of the present study was to update and generalize the extant prospective research using a more representative sample of worldwide airports, a wider range of …

Prediction & Active Control Of Multi-Rotor Noise, Samuel O. Afari

Doctoral Dissertations and Master's Theses

Significant developments have been made in designing and implementation of Advanced Air Mobility Vehicles (AAMV). However, wider applications in urban areas require addressing several challenges, such as safety and quietness. These vehicles differ from conventional helicopter in that they operate at a relatively lower Reynolds number. More chiefly, they operate with multiples of rotors, which may pose some issues aerodynamically, as well as acoustically. The aim of this research is to first investigate the various noise sources in multi-rotor systems. High-fidelity simulations of two in-line counter-rotating propellers in hover, and in forward flight conditions are performed. Near field flow and …

The Linearized Euler Equations For Predicting Supersonic Jet Noise Of A Rectangular Jet Using Openfoam, Patrick Good

Doctoral Dissertations and Master's Theses

This thesis presents a Linearized Euler Equation (LEE) solver that was developed for OpenFOAM. OpenFOAM is an open-source Computational Fluid Dynamics (CFD) package that is widely used by industry and academia. The LEE’s are a set of equations used in Computational Aeroacoustics (CAA). The LEE’s can solve for the acoustic solution directly and quickly. The solver developed, named leeFoam, was tested against analytical solutions to verify accuracy and then was utilized to predict the acoustics of a heated supersonic rectangular jet. The rectangular jet (RJET) results were compared against experimental data.

The results from this work show that OpenFOAM can …

Numerical Modeling Of Synthetic Vortical Disturbance Interactions Using Openfoam, Ahmed Bilal

Doctoral Dissertations and Master's Theses

Nowadays, the number of Advance Air Mobility (AAM) Electic Vertical Take-off and Landing (eVTOL) concepts is rapidly increasing due to their capability of vertical take-off and landing at vertiports located on rooftops of tall urban buildings, which does not require using the ground space in a condensed urban environment. Such flight operations, however, will be greatly affected by the vertiport’s highly unsteady, turbulent flow environment. The goal of this study is to model the turbulent wind interaction with a building to understand the unsteady flow characteristics around vertiports and match the induced unsteady disturbance field to the canonical disturbance forms, …

Application Of Direct Simulation Monte Carlo Method To Computation Of Rf Signal Degradation During Hypersonic Flight, Andrew Derubertis

McKelvey School of Engineering Theses & Dissertations

In order to further understand the hypersonic blackout problem, the first step is to investigate models to quantify signal degradation and begin implementing these models to representative plasma sheath and flow data. This research is the first attempt at implementing a model to predict RF signal degradation through the plasma sheath surrounding the hypersonic air vehicle. The investigation is performed using a Direct Simulation Monte Carlo (DSMC) based flow solver. The dsmcFoam solver in the OpenFoam library is used to simulate the flow around hypersonic bodies to obtain flow field properties, most importantly the electron number density profile, to aid …

On The Simulation Of Supersonic Flame Holder Cavities With Openfoam, Zachary Chapman

Electronic Theses and Dissertations

One of the next major advancements in the aerospace industry will be hypersonic flight. However, to achieve hypersonic flight, propulsion systems capable of reaching hypersonic speeds need to be developed. One of the more promising hypersonic propulsion systems is the scramjet engine, however, several problems still need to be explored before reliable scramjet engines can be produced, the biggest being keeping the engine ignited. This has led to the use of flame holder cavities to create a region of subsonic flow within the engine to allow combustion to occur. High experimental costs make the use of computational fluid dynamic (CFD) …

Comparison Of Dynamics Stability Testing Techniques With Magnetic Suspension Wind Tunnel Capabilities, Otoniel A. Ramirez, Mark Schoenenberger, David E. Cox, Colin P. Britcher

Mechanical & Aerospace Engineering Faculty Publications

Dynamic stability testing techniques currently utilized at NASA Langley Research Center (LaRC) are conducted in multiple facilities and consists of free flight, forced oscillation, and free-to-oscillate tests. The NASA/ODU Magnetic Suspension and Balance System (MSBS) has been recommissioned to explore its utility as an additional facility to expand the dynamic stability test capabilities currently available at NASA LaRC. Simulations were created to replicate each current test facility and method as closely as possible. Data collected from the simulated environments was corrupted with replicated noise sources of the different testing environments and then compared to real data collected during tests when …

Topologically Optimized Electrodes For Electroosmotic Actuation, Jianwen Sun, Jianyu Zhang, Ce Guan, Teng Zhou, Shizhi Qian, Yongbo Deng

Mechanical & Aerospace Engineering Faculty Publications

Electroosmosis is one of the most used actuation mechanisms for the microfluidics in the current active lab-on-chip devices. It is generated on the induced charged microchannel walls in contact with an electrolyte solution. Electrode distribution plays the key role on providing the external electric field for electroosmosis, and determines the performance of electroosmotic microfluidics. Therefore, this paper proposes a topology optimization approach for the electrodes of electroosmotic microfluidics, where the electrode layout on the microchannel wall can be determined to achieve designer desired microfluidic performance. This topology optimization is carried out by implementing the interpolation of electric insulation and electric …

An Evaluation Of Thermocouple Reconstruction Techniques, Derek Brauneis

Electronic Theses and Dissertations, 2020-

Temperature measurements can be difficult to obtain across many different harsh environments such as engine combustion chambers, engine exhaust temperatures, and explosion fireballs. While there are alternate methods to measure fluid temperature such as laser measurements, acoustic measurements, and camera imaging techniques, these methods can often be expensive, difficult to implement, and not able to see within the environment. Thermocouples are popular sensors because they are cheap and easy to implement across a wide range of applications and can measure temperature in areas where other methods cannot reach or see. However, while these sensors are very popular and versatile, they …

The Development Of Computational Models For Melting-Solidification Applications Using The Volume-Of-Fluid Method, Brendon Cavainolo

Electronic Theses and Dissertations, 2020-

Fluids-related issues in the Aerospace industry are often multiphase in scope. Numerical modeling, such as computational fluid dynamics, is used to describe these problems, as they are difficult or impossible to describe analytically. This research uses computational fluid dynamics to describe multiphase problems related to melting-solidification and particle impingement. Firstly, a numerical model was established that uses the Volume-of-Fluid method to resolve a melting/solidifying particle. This model was verified against experiments and simplified analytical models, and a mesh independence study was done to ensure the results were independent of the mesh sizing. Next, the model was applied to two separate …

Heat Release And Flame Scale Effects On Turbulence Dynamics In Confined Premixed Flows, Max Fortin

Electronic Theses and Dissertations, 2020-

As industry transitions to a net-zero carbon future, turbulent premixed combustion will remain an integral process for power generating gas turbines and are also desired for aviation engines due to their ability to minimize pollutant emissions. However, accurately predicting the behavior of a turbulent reacting flow field remains a challenge. To better understand the dynamics of premixed reacting flows, this study experimentally investigates the evolution of turbulence in a high-speed bluff-body combustor. The combustor is operated across a range of equivalence ratios from 0.7-1 to quantify the role of heat release and flame scales on the evolution of turbulence as …

Detonability Of A Rotating Detonation Combustor Seeded With Carbon/Hydrocarbon Particles At Fringe Operating Conditions, Matthew Hopwood

Electronic Theses and Dissertations, 2020-

The Rotating Detonation Combustor (RDC) has, in recent years, been a subject of great interest in the pressure-gain combustion research community. Researchers have been investigating the RDC as a potential improvement over current combustors in today's turbomachinery-based power generation systems. With the theoretical efficiency boost that detonations provide over deflagrating combustors, RDCs have the promise to be a next step in fuel/cost savings in the power generation industry. One mode of research to push an RDCs capabilities is the potential use of combustible carbon/hydrocarbon solid particles in addition to liquid or gaseous fuels. These particles are a source of high …

Rotorcraft Lander Fixed To A Descending Capsule Backshell, Corey Zucker

Electronic Theses and Dissertations, 2020-

NASA is financing a mission to study the surface of Titan, Saturn's largest moon, to investigate the terrain, chemical compositions, and potential for existent life. This mission is an exciting advancement from Mars Ingenuity, because the quadrotor lander, Dragonfly, will be the first of its kind with four coaxial rotors. Upon entry into Titan, and at near surface atmospheric conditions, Dragonfly will exit a parachute supported backshell that has shed its protective heatshield. The aerodynamics of this state are significant in comprehending the dynamics of the overall system for successful deployment into powered flight. The studies presented here examine the …