Engineering Commons^™

Wall-Jet Turbulence And Mixing Control By Way Of A Pulsed Inlet Velocity, Cristale D. Garnica Vallejo

Doctoral Dissertations and Master's Theses

Understanding wall-jet-induced turbulence and mixing is an important challenge in modern engineering, as drag reduction and mixing enhancement are attainable by modifying the flow development. Simulations are performed to investigate the effect on skin friction and flow mixing due to introducing controlled perturbations, at the initial shear layer of a planar wall-jet using jet inlet cyclic pulsing. The billow production by the Kelvin-Helmholtz instability, the instability that drives turbulence in a wall-jet, is modified by the excitation of the inlet velocity profile by a sine wave perturbation. Two types of wall-jet simulations are carried out, a two-dimensional compressible case at …

Development Of A Research Spacecraft Test-Bed With Implementation Of Control Laws To Compensate Undesired Dynamics, Yomary Angélica Betancur Vesga

Doctoral Dissertations and Master's Theses

The development of research spacecraft systems has a significant impact on the preparation and simulation of future space missions. Hardware, software and operation procedures can be adequately tested, validated and verified before they are deployed for the actual mission. In this thesis, a spacecraft vehicle test-bed named Extreme Access System (EASY) was developed. EASY aims at supporting validation and verification of guidance, navigation and control algorithms. Description of EASY spacecraft systems, sub-systems and integration is presented in this thesis along with an analysis of results from numerical simulation and actual implementation of control laws. An attitude control architecture based on …

Effects Of Musical Ability On Flight Planning, Situational Awareness, And Flight Path Deviations, Andrew P. Henry

Doctoral Dissertations and Master's Theses

Numerous studies have been conducted on music education and the benefits that learning an instrument has on the brain. However, there is little research that connects a pilot’s ability to play an instrument to a pilot’s ability to fly an airplane. When learning an instrument, students learn non-musical abilities, such as executive functions, which may correspond with the skills necessary to be a good pilot. The purpose of this study was to find a relationship between learning a musical instrument and pilot performance, specifically related to flight planning, situational awareness, and flight path deviations. This study was a quasi-experimental design …

The Effectiveness Of Augmented Reality For Astronauts On Lunar Missions: An Analog Study, Godfrey Valencio D’Souza

Doctoral Dissertations and Master's Theses

The uses of augmented reality and head-up displays are becoming more prominent in industries such as aviation, automotive, and medicine. An augmented reality device such as the Microsoft HoloLens can project holograms onto the user’s natural field of view to assist with completion of a variety of tasks. Unfortunately, only a little research and development has begun in the space sector for astronauts using these head-up displays. Future lunar missions could incorporate augmented reality for astronauts to ease task load and improve accuracy. This study evaluated the usability, subjective workload, and task performance of 22 participants using the Microsoft HoloLens …

Numerical Treatment Of Schrödinger’S Equation For One-Particle And Two-Particle Systems Using Matrix Method, Spatika Dasharati Iyengar

Doctoral Dissertations and Master's Theses

With an increased interest in accurately predicting aerothermal environments for planetary entry, recent researches have concentrated on developing high fidelity computational models using quantum-mechanical first principles. These calculations are dependent on solving the Schrödinger equation using molecular orbital theory techniques. They are either approximate solutions to actual equations or exact solutions to approximate equations. Exact solutions have not found favor due to the computational expense of the problem. Hence, a novel numerical approach is developed and tested here using linear algebraic matrix methods to enable precise solutions.

The finite-difference technique is used to cast the Time-Independent Schrödinger equation (TISE) in …

In-Situ Measurement Of Resin Shrinkage For Aerospace Components, Samarth Motagi

Doctoral Dissertations and Master's Theses

Resin shrinkage due to chemical changes and thermal gradients plays an important role in the residual stress evolution during composite manufacturing. In this thesis, we develop a new in-situ experimental approach for measuring resin shrinkage during curing with the help of digital image correlation (DIC) instrumented on a specially designed autoclave with borosilicate viewports. The images of the resin sample are captured at regular intervals with the help of DIC to measure the displacement and strains during the curing process. We utilize this method for a comparative analysis of resin shrinkage in two common aerospace epoxies, Epoxy 105 and EPON …

Adaptive Learning Terrain Estimation For Unmanned Aerial Vehicle Applications, Pedro L. Vergara Garcia

Doctoral Dissertations and Master's Theses

For the past decade, terrain mapping research has focused on ground robots using occupancy grids and tree-like data structures, like Octomap and Quadtrees. Since flight vehicles have different constraints, ground-based terrain mapping research may not be directly applicable to the aerospace industry. To address this issue, Adaptive Learning Terrain Estimation algorithms have been developed with an aim towards aerospace applications. This thesis develops and tests Adaptive Learning Terrain Estimation algorithms using a custom test benchmark on representative aerospace cases: autonomous UAV landing and UAV flight through 3D urban environments. The fundamental objective of this thesis is to investigate the use …

Numerical Investigation Of Scaling Effects Of A Ramjet-Powered Projectile, Arjun Jaishankar Vedam

Doctoral Dissertations and Master's Theses

Ramjet flowpath miniaturization is a potentially useful technology for integration into munitions to increase range, accuracy, and lethality. The emphasis of this effort is to numerically characterize the performance of a miniature hydrogen-fueled and ethylene-fueled ramjet flowpath during Mach 3 and Mach 3.5 sea-level flight. The effect of geometric scale on ramjet performance is evaluated using high-fidelity RANS CFD models. Sensitivity to nonequilibrium laminar and turbulence-limited chemistry, and transitional turbulence treatments are evaluated. The physical sources of small scale performance limitations are identified for both fuel types. Finally, flowpath integration for small-scale applications is briefly addressed.

Multirotor Uas Sense And Avoid With Sensor Fusion, Jonathan Mark Buchholz

Doctoral Dissertations and Master's Theses

In this thesis, the key concepts of independent autonomous Unmanned Aircraft Systems (UAS) are explored including obstacle detection, dynamic obstacle state estimation, and avoidance strategy. This area is explored in pursuit of determining the viability of UAS Sense and Avoid (SAA) in static and dynamic operational environments. This exploration is driven by dynamic simulation and post-processing of real-world data. A sensor suite comprised of a 3D Light Detection and Ranging (LIDAR) sensor, visual camera, and 9 Degree of Freedom (DOF) Inertial Measurement Unit (IMU) was found to be beneficial to autonomous UAS SAA in urban environments. Promising results are based …

Fuel Efficient Control Design And Constrained Motion Analysis For Spacecraft Coulomb Formation In Elliptic Chief Orbits, Muhammad Wasif Memon

Doctoral Dissertations and Master's Theses

The use of Coulomb force has been analyzed in recent years to provide propulsion in space for various applications. Coulomb formation can also be utilized to make close formation spacecraft missions fuel efficient. In this study, the Coulomb formation of two craft is studied in elliptic chief orbits for two formation geometries. The first formation requires both spacecraft to be aligned along the nadir (radial) direction and the second formation requires both spacecraft to maintain a constant separation distance relative to each other while each spacecraft rotates freely on the surface of a sphere with the ratio of the radii …

A Step Toward Ending Long Airport Security Lines: The Modified Boarding Pass, Joel Lee

Doctoral Dissertations and Master's Theses

Anyone who has traveled by air has most likely experienced long airport security lines. Yet not much is known about its cause because few have considered if passengers have created this problem for themselves. The present study attempts to fill this research gap by suggesting that when passengers are not well-prepared for security screening, they delay the process by making mistakes and not complying with procedures. This lack of preparedness can be attributed to several shortcomings of security signposts. This study proposes the use of a modified boarding pass as an alternative form of signage to help passengers better prepare …

Autonomous Autorotation Of A Tilt-Rotor Aircraft Using Model Predictive Control, Elias Wilson

Doctoral Dissertations and Master's Theses

Tilt rotor vehicles are governed by FAA laws also used for conventional helicopters, which require autorotational maneuvering and landing given a total power failure. With low inertia rotors and high disk loading of tilt rotor vehicles, this already difficult task becomes significantly more challenging. In this work, a model predictive controller is developed to autonomously maneuver and land a tilt rotor given complete power loss. A high fidelity model of a tilt rotor vehicle is created and used to simulate the vehicle dynamics and response to control inputs. A reduced order dynamic model is used within a model predictive control …

Fuel Shortages During Hurricanes: Epidemiological Modeling And Optimal Control, Sabique Ul Islam

Doctoral Dissertations and Master's Theses

Hurricanes are powerful agents of destruction with significant socioeconomic impacts. A persistent problem due to the large-scale evacuations during hurricanes in the southeastern United States is the fuel shortages during the evacuation. Fuel shortages often lead to stranded vehicles and exacerbate the evacuation efforts. Computational models can aid in emergency preparedness and help mitigate the impacts of hurricanes. In this thesis, the hurricane fuel shortages are modeled using the Susceptible-Infected-Recovered (SIR) epidemic model. Crowd-sourced data corresponding to Hurricane Irma and Florence are utilized to parametrize the model. An estimation technique based on Unscented Kalman filter (UKF) is employed to evaluate …

Computational Model For Pedestrian Movement And Infectious Diseases Spread During Air Travel: A Molecular Dynamics-Like Numerical Approach, Pierrot Derjany

Doctoral Dissertations and Master's Theses

There is direct evidence of the transmission of fatal infectious pathogens in large human gatherings. Air transportation is no exception. The mixing of susceptible and infectious individuals in this high-density man-made environment involves pedestrian movement which is generally not taken into account in modeling studies of disease dynamics. This thesis addresses this problem through a multiscale model that combines pedestrian dynamics with stochastic infection spread models. This generic model is applicable to several directly transmitted diseases. Through this multiscale framework, the effectiveness of certain layout and strategies in suppressing the disease spread in highly crowded locations such as airplanes, airports …

Large Deformable Soft Actuators Using Dielectric Elastomer And Origami Inspired Structures, Jangho Park

Doctoral Dissertations and Master's Theses

There have been significant developments in the field of robotics. Significant development consists of new configurations, control mechanisms, and actuators based upon its applications. Despite significant improvements in modern robotics, the biologically inspired robots has taken the center stage. Inspired by nature, biologically inspired robots are called ‘soft robots’. Within these robots lies a secret ingredient: the actuator. Soft robotic development has been driven by the idea of developing actuators that are like human muscle and are known as ‘artificial muscle’. Among different materials suitable for the development of artificial muscle, the dielectric elastomer actuator (DEA) is capable of large …

Design And Performance Of A Communications System For A Low-Cost High Altitude Balloon Platform For Troposphere And Stratosphere Research, Noemí Miguélez Gómez

Doctoral Dissertations and Master's Theses

AFOSR Multidisciplinary University Research Initiative (MURI), "Integrated Measurement and Modeling Characterization of Stratospheric Turbulence", is a 5-year effort to resolve significant operational issues concerning hypersonic vehicle aerothermodynamics, boundary layer stability, and aero-optical propagation. In situ turbulence measurements along with modeling will quantify spatiotemporal statistics and the dependence of stratospheric turbulence on underlying meteorology to a degree not previously possible. Data from high altitude balloons sampling up to kHz is required to characterize turbulence to the inner-scale, or smaller, over paltitudes from 20 km to 35+ km.

This thesis presents the development of a standard balloon bus, based on reliable COTS …

Efficient Privacy-Aware Imagery Data Analysis, Yifan Tian

Doctoral Dissertations and Master's Theses

The widespread use of smartphones and camera-coupled Internet of Thing (IoT) devices triggers an explosive growth of imagery data. To extract and process the rich contents contained in imagery data, various image analysis techniques have been investigated and applied to a spectrum of application scenarios. In recent years, breakthroughs in deep learning have powered a new revolution for image analysis in terms of effectiveness with high resource consumption. Given the fact that most smartphones and IoT devices have limited computational capability and battery life, they are not ready for the processing of computational intensive analytics over imagery data collected by …

Temporal-Spatial Analysis Of Emergency Evacuation Traffic, Lorraine Margot Acevedo Loreto

Doctoral Dissertations and Master's Theses

Mass evacuations, particularly those at a statewide level, represent the largest single-event traffic movements that exist. These complex events can last several days, cover thousands of miles of roadway, and include hundreds of thousands of people and vehicles. Often, they are also marked by enormous delay and congestion and are nearly always criticized for their inefficiency and lack of management. However, there are no standardized methods by which to systematically quantify traffic characteristics at the proper scale. This paper describes research to develop and apply an analytical method to measure and describe statewide mass-evacuations in a practical, cost-effective manner. The …

A Data Mining Methodology For Vehicle Crashworthiness Design, Xianping Du

Doctoral Dissertations and Master's Theses

This study develops a systematic design methodology based on data mining theory for decision-making in the development of crashworthy vehicles. The new data mining methodology allows the exploration of a large crash simulation dataset to discover the underlying relationships among vehicle crash responses and design variables at multiple levels and to derive design rules based on the whole-vehicle safety requirements to make decisions about component-level and subcomponent-level design. The method can resolve a major issue with existing design approaches related to vehicle crashworthiness: that is, limited abilities to explore information from large datasets, which may hamper decision-making in the design …

Assessing Impacts Of Decentralizing Airpower Command And Control, Allen Goodwin Peck

Doctoral Dissertations and Master's Theses

Centralized control is a fundamental tenet of joint airpower doctrine, yet there are operational situations in which some degree of decentralization may be appropriate. The purpose of this research was to quantitatively assess the impacts of decentralizing the command and control (C2) of airpower under varying operational conditions. The research used the experimental method to test hypotheses regarding decentralization of control. JAEX, a stochastic, attrition-based Blue-versus-Red war gaming model, generated the required data.

The mean difference between JAEX outcomes under centralized control and outcomes under decentralized control constituted the dependent variable for each experiment. The independent variables were the operational …

Risk Mitigation For Low Latitude Ground-Based Augmentation System (Gbas) Precision Approach Operations, Richard Walter Cole

Doctoral Dissertations and Master's Theses

The ground-based augmentation system (GBAS) is a safety-critical system consisting of the hardware and software that augments the Global Positioning System (GPS) to provide precision approach and landing capability and is one of the navigational cornerstones of the International Civil Aviation Organization's (ICAO) global transition to space-based technologies. In low latitude regions, where the space-based augmentation system (SBAS) cannot provide adequate precision approach service due to large system errors induced by ionospheric delays, GBAS is the best option to provide the primary navigation function for the modernized global air traffic system. The purpose of the study was to identify patterns …

Multimode Nonlinear Vibration Analysis Of Stiffened Functionally Graded Double Curved Shells In A Thermal Environment, Boutros Azizi

Doctoral Dissertations and Master's Theses

The motivation of the current work is to develop a multi-modal analysis of the nonlinear response of stiffened double curved shells made of functionally graded materials under thermal loads. The formulation is based on the first order shear deformation shell theory in conjunction with the von Kármán geometrical nonlinear strain-displacement relationships. The nonlinear equations of motion of stiffened double curved shell based on the extended Sanders’s theory were derived using Galerkin’s method. The resulting system of infinite nonlinear ordinary differential equations, that includes both cubic and quadratic nonlinear terms, was solved using a nonlinear dynamic software XPPAUT to obtain the …

Thermal Bending, Buckling And Post-Buckling Analysis Of Unsymmetrically Laminated Composite Beams With The Effects Of Moisture And Geometric Imperfections, Claudia Barreno

Doctoral Dissertations and Master's Theses

This thesis is concerned with the analytical study of the thermal bending, buckling, and post-buckling of unsymmetrically laminated composite beams with imperfection under hygrothermal effects. Three different boundary conditions will be considered on this study. The non-linear governing partial differential equations are derived by taking into account the von-Karman geometrical nonlinearity for an imperfect unsymmetrical laminated composite beam. Classical beam theory (CBT) as well as first order shear deformation theory (FSDT) will be used. The effects of temperature, angle of orientation, moisture variations, imperfection, and geometrical parameters, will be evaluated and discussed. Two different laminated composite laminates will be considered: …

Hybrid Structural Composites With Energy Harvesting Capabilities, Simon Furnes

Doctoral Dissertations and Master's Theses

Hybrid materials have received significant interest due to the potential enhancements they provide over traditional materials such as sensing, actuating, energy scavenging, thermal management, and vibration damping. While traditional materials can be utilized for either one of these functions or loadbearing, the hybrid materials are superior as they allow combination of a wide array of functionalities whilst being suitable for load-bearing purposes.

The goal of this thesis is to elucidate the synergistic effects of hybridization of two piezoelectric materials; zinc oxide nanowires (ZnO NWs) and thin film of lead zirconium titanate (PZT) on the mechanical and energy harvesting of beams …

A Volume-Force Synthetic Disturbance Approach For High-Fidelity Of Unsteady Fluid Structure Interactions, Marina Kazarina

Doctoral Dissertations and Master's Theses

The purpose of this dissertation is to analyze the momentum source model, for generating synthetic vortical disturbance field in numerical simulations of unsteady fluid-structure interactions, access limitations of this approach, to find requirements for the computational domain, space and time resolution, and apply this model to investigate selected physical problems. For this reason a comprehensive parametric study of volume-force based method of generating spectral synthetic turbulence inside the computational domain is conducted first. The method is then extended to synthesize turbulence with arbitrary energy spectrum. The synthetic turbulence is generated through momentum source terms in Navier-Stokes equations, and the developed …

Feasibility Of Circular Orbits For Proximity Operations In Strongly Perturbed Environments Around Uniformly Rotating Asteroids, Nicholas Peter Liapis

Doctoral Dissertations and Master's Theses

Asteroids have been mapped and observed since 1801 when an Italian astronomer Guiseppe Piazzi discovered Ceres (Serio, Manara, & Sicoli, 2002). Since then, asteroids have been growing in popularity throughout the scientific community because they are thought to hold the information we need to understand how the solar system developed and why life exists on earth, as well as potential precious resources. This research studies different types of orbits that have been performed to date around asteroids and how they can be reworked to require less control effort. Different types of missions that have been sent to asteroids are discussed, …

Prediction Of Noise Associated With An Isolated Uav Propeller, Samuel O. Afari

Doctoral Dissertations and Master's Theses

The emergent field of interest in the Urban Air Mobility community is geared towards a world where aerial vehicles are commonplace. This poses the problem of the effects of the radiated noise. The present research presents an in-depth analysis of the noise generation mechanism of a propeller as a mode of propulsion of the said aerial vehicles. Numerical simulation utilizing a Hybrid Large-Eddy Simulation (LES) coupled with Unsteady Reynolds-Averaged Navier-Stokes (RANS) solver, is adopted on an isolated propeller modeled from the commercial DJI Phantom II 9450 propeller. The Spalart-Allmaras one equation turbulence model with rotation/curvature correction is used. The Farassat’s …

Benefits Of Additional Runway Crossings On Parallel Runway Operations, Sergio Ezequiel Taleisnik

Doctoral Dissertations and Master's Theses

As the air transportation industry expands, airports face numerous challenges to manage the increasing traffic. Among these problems, runway crossings are a considerable source of ground traffic inefficiency and risk. Building end-around taxiways are the only strategy to avoid crossings, but these are not always feasible, and therefore airport planners must find alternatives. This study consisted of a simulation over an airport that currently requires a vast amount of its arrivals to go through runway crossings in order to reach the apron; the airport simulation software utilized was the Total Airspace and Airport Modeler (TAAM). The process began with a …

Spacecraft Trajectory Planning For Optimal Observability Using Angles-Only Navigation, Francisco José Franquiz

Doctoral Dissertations and Master's Theses

This work leverages existing techniques in angles-only navigation to develop optimal range observability maneuvers and trajectory planning methods for spacecraft under constrained relative motion. The resulting contribution is a guidance method for impulsive rendezvous and proximity operations valid for elliptic orbits of arbitrary eccentricity.

The system dynamics describe the relative motion of an arbitrary number of maneuvering (chaser) spacecraft about a single non-cooperative resident-space-object (RSO). The chaser spacecraft motion is constrained in terms of the 1) collision bounds of the RSO, 2) maximum fuel usage, 3) eclipse avoidance, and 4) optical sensor field of view restrictions. When more than one …

A Behavioral Research Model For Small Unmanned Aircraft Systems For Data Gathering Operations, Paul Leonard Myers Iii

Doctoral Dissertations and Master's Theses

According to Hitlin (2017) of the Pew Research Center, only 8% of U.S. citizens own an unmanned aircraft. Additionally, regarding feelings if U.S. citizens saw an unmanned aircraft flying close to where they live, 26% say they would be nervous, 12% feel angry, and 11% are scared. As of March 9, 2018, there were 1,050,328 U.S. small unmanned aircraft system (sUAS) registrations compared to 947,970 November 29, 2017. While sUAS use has increased in the U.S., it has lagged when compared to other items for personal use available to U.S. citizens as 92% own cell phones (Anderson, 2015). This slower …