Aerodynamics and Fluid Mechanics Commons^™

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, …

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 …

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 …

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 …

Numerical Study Of Owls’ Leading-Edge Serrations, Asif Shahriar Nafi

Electronic Theses and Dissertations

The silent flight ability of owls is often attributed to their unique wing morphology and its interaction with their wingbeat kinematics. Among these distinctive morphological features, leading-edge serrations stand out – these are rigid, miniature, hook-like patterns located at the leading edge of the primary feathers of their wings. It had been hypothesized that these leading-edge serrations serve as a passive flow control mechanism, influencing the aerodynamic performance and potentially affecting the boundary layer development over the wing, subsequently influencing wake flow dynamics. Despite being the subject of research spanning multiple decades, a consensus regarding the aerodynamic mechanisms underpinning owls’ …

Stratospheric Glider Measurements Of Atmospheric Parameters, Anisa Haghighi

Theses and Dissertations--Mechanical Engineering

In June 2021 a series of high altitude flights were conducted in Spaceport America, NM, using a balloon launched Uncrewed Aircraft System (UAS) to assess its capability to conduct measurements of various atmospheric properties and study turbulence in the troposphere and lower stratosphere. This UAS descends using an automated flight trajectory. The instruments aboard included a NASA-developed infrasonic microphone to evaluate its remote turbulence detection capabilities and a five-hole probe capable of measuring the in situ wind vector. Also on board were temperature, humidity and wind profile sensors. This document focuses on the atmospheric properties measured at high altitudes, the …

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 …

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 …

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 …

Underwater Communication Acoustic Transducers: A Technology Review, Laila Shams, Tian-Bing Xu, Zhongqing Su (Ed.), Branko Glisic (Ed.), Maria Pina Limongelli (Ed.)

Mechanical & Aerospace Engineering Faculty Publications

This paper provides a comprehensive review on transducer technologies for underwater communications. The popularly used communication transducers, such as piezoelectric acoustic transducers, electromagnetic acoustic transducers, and acousto-optic devices are reviewed in detail. The reasons that common air communication technologies are invalid die to the differences between the media of air and water are addresses. Because of the abilities to overcome challenges the complexity of marine environments, piezoelectric acoustic transducers are playing the major underwater communication roles for science, surveillance, and Naval missions. The configuration and material properties of piezoelectric transducers effects on signal output power, beamwidth, amplitude, and other properties …

Convolutional-Neural-Network-Based Des-Level Aerodynamic Flow Field Generation From Urans Data, John P. Romano, Oktay Baysal, Alec C. Brodeur

Mechanical & Aerospace Engineering Faculty Publications

The present paper culminates several investigations into the use of convolutional neural networks (CNNs) as a post-processing step to improve the accuracy of unsteady Reynolds-averaged Navier–Stokes (URANS) simulations for subsonic flows over airfoils at low angles of attack. Time-averaged detached eddy simulation (DES)-generated flow fields serve as the target data for creating and training CNN models. CNN post-processing generates flow-field data comparable to DES resolution, but after using only URANS-level resources and properly training CNN models. This document outlines the underlying theory and progress toward the goal of improving URANS simulations by looking at flow predictions for a class of …

An Optimization Study Of Small-Scale Propeller Blade, Fahad M. Nabid

Honors Undergraduate Theses

This research paper aims to investigate the optimization of smaller propeller blades to achieve maximum efficiency by studying the effect of the twist angle on reducing drag, increasing thrust, and preventing rapid wear on the blade. Inefficient propellers consume a significant amount of energy, particularly during low-speed flights. The low Reynolds number regime challenges aviation engineers to design propellers with the highest possible efficiency to minimize energy losses. The primary objective of this thesis is to optimize smaller propeller blade shapes to enable them to produce maximum efficiency. The advanced ratio of a propeller blade heavily influences the blade's performance …

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 …

Hypersonic Aero-Optic Measurements In A High-Pressure Shock Tube, Jonathan P. Mcgaunn

Graduate Thesis and Dissertation 2023-2024

The high-pressure shock tube facility (HiPER-STAR) at the University of Central Florida (UCF) is analyzed experimentally to demonstrate the practicality of hypersonic aero-optical testing in an impulse facility without the use of an expansion nozzle or acceleration tube. The investigation analyses driver gas blending with helium and hydrogen to raise the speed of sound ratio in an attempt to increase the Mach number for aero-optics testing. HiPER-STAR has a unique ability to withstand pressures up to 1000 atm and run in a double diaphragm configuration allowing for a significant pressure differential to be created between the driver and driven sections. …

Thermal Management Strategies For Hypersonic Flight: Supercritical Co2 Jet Impingement Cooling Investigation For Leading Edge, Manoj Prabakar Sargunaraj

Graduate Thesis and Dissertation 2023-2024

This study addresses the critical need for effective thermal management in hypersonic vehicles facing intense heat at their leading edge due to high enthalpy flow. The objective is to propose an active impingement cooling system that ensures the structural stability and performance of these vehicles. This dissertation presents an in-depth exploration of the numerical simulations conducted on the hypersonic leading edge, focusing on a 3mm radius with active cooling utilizing supercritical carbon dioxide (sCO2) as the coolant. The research incorporates conjugate simulations that merge external hypersonic flow and sCO2 active cooling. Utilizing a thermodynamic non-equilibrium two-temperature model and various chemical …

The Numerical Study Of Aeroacoustics Performance Of Wings With Different Wavelength Leading-Edge Tubercles, Youjie Zhang

Honors Undergraduate Theses

The leading-edge tubercle is a type of airfoil modification that inspired by the humpback whale. It was found that the aerodynamic performance of the wing would increase compared to the wing without tubercles. In the past several years, a lot of numerical and experimental studies have been accomplished to explore this leading-edge modification. Besides the aerodynamic performance change, this research explores the aeroacoustics behavior of airfoils with leading-edge tubercles. A numerical study based on Computational Fluid Dynamics (CFD) is established, and simulations using Star CCM are accomplished based on reasonable set-ups. The airfoil chosen to create the wing is NACA …

Numerical Study Of The Time-Periodic Electroosmotic Flow Of Viscoelastic Fluid Through A Short Constriction Microchannel, Jianyu Ji, Shizhi Qian, Armani Marie Parker, Xiaoyu Zhang

Mechanical & Aerospace Engineering Faculty Publications

Electroosmotic flow (EOF) is of utmost significance due to its numerous practical uses in controlling flow at micro/nanoscales. In the present study, the time-periodic EOF of a viscoelastic fluid is statistically analyzed using a short 10:1 constriction microfluidic channel joining two reservoirs on either side. The flow is modeled using the Oldroyd-B (OB) model and the Poisson-Boltzmann model. The EOF of a highly concentrated polyacrylamide (PAA) aqueous solution is investigated under the combined effects of an alternating current (AC) electric field and a direct current (DC) electric field. Power-law degradation is visible in the energy spectra of the velocity fluctuations …

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 …

Impact Of Spallation And Internal Radiation On Fibrous Ablative Materials, Raghava Sai Chaitanya Davuluri

Theses and Dissertations--Mechanical Engineering

Space vehicles are equipped with Thermal Protection Systems (TPS) that encounter high heat rates and protect the payload while entering a planetary atmosphere. For most missions that interest NASA, ablative materials are used as TPS. These materials undergo several mass and energy transfer mechanisms to absorb intense heat. The size and construction of the TPS are based on the composition of the planetary atmosphere and the impact of various ablative mechanisms on the flow field and the material. Therefore, it is essential to quantify the rates of different ablative phenomena to model TPS accurately. In this work, the impact of …