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Articles 1 - 26 of 26
Full-Text Articles in Aerospace Engineering
Contributions To The Understanding Of Turbulent Boundary Layers Over Curved Walls, Nicholas Zhu
Contributions To The Understanding Of Turbulent Boundary Layers Over Curved Walls, Nicholas Zhu
Doctoral Dissertations and Master's Theses
A wind tunnel campaign was conducted to investigate the DARPA Suboff boundary layer. To emphasize the axisymmetric boundary layer, the generic submarine model's sail, appendages, and propeller were omitted. The study focused on the afterbody from 70–95% of the model length to examine the concurrent pressure gradient and wall curvature effects, which are commonplace in engineering. Three particle image velocimetry (PIV) configurations were employed to measure the boundary layer in detail: one spanned the entire afterbody, another had narrow strips sampled at 16 kHz, and the third used two simultaneous orthogonal measurement planes. Considerable effort was made to reduce the …
Heat Transfer To Arrays Of Oscillating Impingement Jets, Alex Q. Clay
Heat Transfer To Arrays Of Oscillating Impingement Jets, Alex Q. Clay
Doctoral Dissertations and Master's Theses
In gas turbine engines, the desire to increase turbine entry temperatures has become more relevant in order to increase engine efficiency. However, materials used in these engines can only withstand temperatures that are so high. Because of this, the ability to cool hot section components will always limit operating temperatures. Impingement cooling jets have become a common way of cooling due to the high rates of heat transfer that can be achieved. However, previous research has shown that the interaction of impingement jets with cylinder wake can improve the intensity and uniformity of heat transfer. The goal of this study …
Bi-Modal Excitation Of A Supersonic Rectangular Jet, Benjamin Malczewski
Bi-Modal Excitation Of A Supersonic Rectangular Jet, Benjamin Malczewski
Doctoral Dissertations and Master's Theses
This work addresses the issue of supersonic rectangular jet noise via bi-modal excitation. A Mach 1.5 heated rectangular jet with a 2:1 aspect ratio is considered. Theoretical work is presented in which a Reduced-Order Model (ROM) is used in conjunction with the Linearized Euler Equations to predict the nonlinear growth and decay of various frequencies due to the interaction between harmonically related modes and the mean flow. Scope is limited to a symmetric disturbance. The case of no interaction is used to help identify a dominant coherent structure, referred to as “f”. For the symmetric disturbance, a Strouhal number of …
Space Radiation Assessment And Mitigation: Meeting The Growing Demand For Shielding Solutions By Enhancing Models And Exploring Novel Shielding Opportunities, M. Laura Sorgi Johann
Space Radiation Assessment And Mitigation: Meeting The Growing Demand For Shielding Solutions By Enhancing Models And Exploring Novel Shielding Opportunities, M. Laura Sorgi Johann
Doctoral Dissertations and Master's Theses
The rapid growth of satellite technology and the increasing presence of vulnerable technology and human life in space have highlighted the need for improved shielding materials. Industry standard protocols for shielding are being pushed to their limits as we gain a deeper understanding of the harsh space environment and as chip sizes approach the scale of radiation wavelengths. Furthermore, the commercialization of space is attracting interest from industries such as pharmaceuticals and semiconductor crystal growing, as they explore the potential benefits of zero-gravity production environments. However, the eagerness to develop lighter shielding and the lack of consideration for existing tools …
Optimization Of A Plate Beam System For Energy Harvesting Using A Piezoelectric Material, Jose Manuel Almendros Espantaleon
Optimization Of A Plate Beam System For Energy Harvesting Using A Piezoelectric Material, Jose Manuel Almendros Espantaleon
Doctoral Dissertations and Master's Theses
With a continuously growing demand for power, driven by the need to reduce our environmental footprint, this research provides an examination of the potential of energy harvesting with smart materials technology and its practical applications. The energy harvesting system considered here works on generating energy through vibrations of a piezoelectric material beam which will undergo sustained vibrations due to flow of air over its surface. It is assumed that sustained limit cycle oscillations of this system will occur at the flutter velocity. This research creates an optimization framework to obtain the best values of parameters that will result in the …
Assessing The Impact Of Spacecraft Fragmentation In The Cislunar Region, Marta Lopez Castro
Assessing The Impact Of Spacecraft Fragmentation In The Cislunar Region, Marta Lopez Castro
Doctoral Dissertations and Master's Theses
In the last decades, space missions have followed great advancements due to technological improvements and the extensive research developed in the field. Some of these missions are increasingly focusing on satellites orbiting the Moon. The Cislunar region is known to have a higher non-linear chaotic component in the dynamics compared to the low-Earth environment. This research is focused on studying the impact that a satellite explosion has in the Cislunar vicinity. The study is conducted for different periodic orbits that are key destinations for Cislunar traffic. By varying the initial conditions, simulations of explosions at different locations of the orbits …
Additively Manufactured Flexible Piezoelectric Wave-Based Multifunctional Sensor, Rishikesh Srinivasaraghavan Govindarajan
Additively Manufactured Flexible Piezoelectric Wave-Based Multifunctional Sensor, Rishikesh Srinivasaraghavan Govindarajan
Doctoral Dissertations and Master's Theses
The demand for acoustic wave-based sensors has rapidly increased in the aerospace, chemical, gas, and biological fields due to their versatility in sensing measurands. This study aims to develop a flexible piezoelectric sensor exhibiting enhanced piezoelectric properties using additive manufacturing techniques that can detect mechanical strains and gas or volatile organic compounds (VOCs) by incorporating functional material into the sensing layer. This research explores piezoelectric substrate fabrication through diverse additive manufacturing techniques, including new material development made of polymer/nano-fillers with electrodes that are filled using different printing techniques. Notably, the design of the interdigital transducer (IDT) in the piezoelectric sensor …
Sliding Mode Control With Chattering Reduction, Suryamshu Ramesh
Sliding Mode Control With Chattering Reduction, Suryamshu Ramesh
Doctoral Dissertations and Master's Theses
Sliding Mode Control is a powerful nonlinear control methodology that can handle parametric uncertainties and external disturbances. However, the discontinuous and high-frequency switching nature of the control law introduces the chattering phenomenon, which leads to potential actuator degradation, alterations to the desired response characteristics and, sometimes, instability during control implementation. The main objective of this thesis is to study Sliding Mode Control with chattering reduction. The Sliding Mode Control law involves an equivalent control component and a discontinuous control component. A disturbance estimation is performed based on Lyapunov analysis and adaptive control techniques and then included in the control law …
Analysis Of Wingtip Vortex Structure Generated By Bio-Inspired Winglets, D'Zahn A. Smith
Analysis Of Wingtip Vortex Structure Generated By Bio-Inspired Winglets, D'Zahn A. Smith
Doctoral Dissertations and Master's Theses
Bio-inspired winglets were studied with the goal of better understanding the structure of the wingtip vortices they generate. Measurements of the tip vortex were previously carried out using stereoscopic particle image velocimetry (sPIV). The bio-inspired winglet was tested on a rectangular NACA 0012 wing section at a 5-degree angle of attack and at a chord Reynolds number of 900,000. Velocity field measurements were recorded at 0.7 and 2 chord lengths aft of the wing’s trailing edge. Compared to the wing with no attachment and a traditional blended winglet, the bio-inspired winglet’s vortex exhibited significantly less intense flow field properties. These …
Characterization And Analysis Of Supersonic Flow Through De Laval Nozzles At Varied Design Conditions, Sarah Baird
Characterization And Analysis Of Supersonic Flow Through De Laval Nozzles At Varied Design Conditions, Sarah Baird
Doctoral Dissertations and Master's Theses
A combined numerical and experimental investigation of supersonic planar nozzles under different design conditions has been conducted. Supersonic planar nozzles are common geometries observed in supersonic wind tunnels and aircraft or rocket engines. For the important role they play in wind tunnel testing and aircraft propulsion, it is important to conduct a thorough numerical and experimental study to characterize their performance at different operating conditions. In this study, a de Laval nozzle was scanned to extract its contours and subsequently modeled to compare analytical and numerical performance expectations under design and off-design conditions. The nozzle was then installed in a …
Modeling Of Rotor Wake Vortex Dynamics And Interactions In Non-Homogenous Vertiport Environments, Garrison P. Shaw
Modeling Of Rotor Wake Vortex Dynamics And Interactions In Non-Homogenous Vertiport Environments, Garrison P. Shaw
Doctoral Dissertations and Master's Theses
The current research serves to analyze and study the effects ground forces can have on the thrust performance of a propeller in multiple different configurations. The current research utilizes an open source Computational Fluid Dynamics (CFD) software known as OpenFOAM to generate calculate and visualize these runs. The model used for this experiment is a hybrid model that employs both a Unsteady Reynolds-Averaged Navier-Stokes (URANS) and a detached eddy simulation using a hybrid Large Eddy Simulation (LES) via a KomegaSSTDDES model. This model serves to save computational time as well as allow for accurate results. The three cases run are …
Machine Learning-Based Gps Jamming And Spoofing Detection, Alberto Squatrito
Machine Learning-Based Gps Jamming And Spoofing Detection, Alberto Squatrito
Doctoral Dissertations and Master's Theses
The increasing reliance on Global Positioning System (GPS) technology across various sectors has exposed vulnerabilities to malicious attacks, particularly GPS jamming and spoofing. This thesis presents an analysis into detection and mitigation strategies for enhancing the resilience of GPS receivers against jamming and spoofing attacks. The research entails the development of a simulated GPS signal and a receiver model to accurately decode and extract information from simulated GPS signals. The study implements the generation of jammed and spoofed signals to emulate potential threats faced by GPS receivers in practical settings. The core innovation lies in the integration of machine learning …
Development Of Eagle3d Solver For Wall Modeled Les Of Transonic Flows, Spencer Moore
Development Of Eagle3d Solver For Wall Modeled Les Of Transonic Flows, Spencer Moore
Doctoral Dissertations and Master's Theses
Wall modeled Large Eddy Simulation (LES) is an area of interest due to its ability to lower computational costs of LES simulation. Even with the application of wall models, LES still proves to have practicality issues when it comes to use in industry, due to the expertise, time, and computational resources required to get results. A case described by an axisymmetric transonic bump is explored utilizing the Embry-Riddle Aeronautical Universities in house unstructured finite volume multi-element CFD code, Eagle3D. Eagle3D, has been brought to the state of the art and validated against current research using this transonic bump case as …
Ti Nano Powder Speckle Pattern Creation And Use In Dic Of Zno Modified Single Carbon Fibers, James Matthew Harris
Ti Nano Powder Speckle Pattern Creation And Use In Dic Of Zno Modified Single Carbon Fibers, James Matthew Harris
Doctoral Dissertations and Master's Theses
As the use of composites continues to grow across aerospace, naval, automotive, construction, 3D printing, and other countless industries, so does the desire to continuously improve their mechanical properties. Improving the adherence of the fiber-matrix interface is one important step for amplifying the capabilities of composites. Work has been performed in modifying carbon fibers by growing zinc oxide (ZnO) nanorods in the fiber surface using a hydrothermal approach, increasing interfacial area and fiber-matrix friction. Macroscale evaluation has shown that the interfacial modification decreases the inter-ply movement and reduces the processing strains and residual stresses. To fully understand the mechanism taking …
Implementation Of Path Planning Methods To Detect And Avoid Gps Signal Degradation In Urban Environments, Ayush Raminedi
Implementation Of Path Planning Methods To Detect And Avoid Gps Signal Degradation In Urban Environments, Ayush Raminedi
Doctoral Dissertations and Master's Theses
In the modern world, various missions are being carried out under the assistance of autonomous flight vehicles due to their ability to operate in a wide range of flight conditions. Regardless, these autonomous vehicles are prone to GPS signal loss in urban environments due to obstructions that cause scintillation, multi-path, and shadowing. These effects that decrease the GPS functionality can deteriorate the accuracy of GPS positioning causing losses in signal tracking leading to a decrease in navigation performance. These effects are modeled into the simulation environment and are used as part of the path planning algorithm to provide better navigation …
Numerical Study In Wind Energy Extraction From Controlled Limit-Cycle Oscillations In Modified Glauert Airfoil, Ethan L. Deweese
Numerical Study In Wind Energy Extraction From Controlled Limit-Cycle Oscillations In Modified Glauert Airfoil, Ethan L. Deweese
Doctoral Dissertations and Master's Theses
Typically, wind energy harvesting technology employs wind turbines. Towards the goal of meeting increasing energy needs with renewable energy sources a novel wind energy harvesting scheme is considered, utilizing a modified Glauert (MG) airfoil experiencing aeroelastic limit cycle oscillation (LCO) from which energy may be extracted. Synthetic jet actuators (SJA)s are used along with the unique geometry of the MG airfoil to control flow separation and amplify the LCO and energy generation potential of the system. The discussed wind energy harvesting scheme could provide flexibility in allowing installations previously unsuitable to wind turbines due to geometric or low wind velocity …
Mitigating Engine Unstart In Scramjets With Porous Bleeders, Ryan Lindley
Mitigating Engine Unstart In Scramjets With Porous Bleeders, Ryan Lindley
Doctoral Dissertations and Master's Theses
The effectiveness of porous bleeders in mitigating unstart phenomena and enhancing isolator effectiveness in a hypersonic scramjet was investigated. Through computational fluid dynamics simulations, the impact of porous bleeder design parameters such as pressure jump coefficient and bleeder size on isolator effectiveness and unstart prevention was evaluated. Results indicated that porous bleeders delayed flow separation and reduced adverse pressure gradients, thereby enhancing isolator performance. Additionally, porous bleeders demonstrated promising capabilities in preventing full unstart events and mitigating oscillatory unstart phenomena.
Conceptual Design Methodology For The Fan-In-Wing Vtol Aircraft, Brock Steinfeldt
Conceptual Design Methodology For The Fan-In-Wing Vtol Aircraft, Brock Steinfeldt
Doctoral Dissertations and Master's Theses
The Fan-In-Wing (FIW) aircraft concept is one of the most compelling solutions for missions demanding jet-like cruise speeds and Vertical TakeOff and Landing (VTOL) capability. However, despite years of interest and documented improvements in lift-fan technology, there exists little in the way of an adequate theory for conceptual design of a fan-in-wing aircraft. To address this issue, a general conceptual design methodology has been developed as a source of guidance for the FIW designer. Through this work, the top-level requirements ranking the fan-in-wing concept above other VTOL aircraft have been defined, while a cross-comparison between the FIW concept and conventional …
Starfish: A Compact, Biomimetic, And Adaptive Shape Memory Alloy Orbital Debris Remover, Katelyn Branaman
Starfish: A Compact, Biomimetic, And Adaptive Shape Memory Alloy Orbital Debris Remover, Katelyn Branaman
Doctoral Dissertations and Master's Theses
This thesis aims to turn the tides on the orbital debris issue through the fabrication and demonstration of a compact, biomimetic, and adaptive shape memory alloy actuated orbital debris remover. The design, referred to as Starfish, is discussed in detail along with its fabrication process and object capture ability. A hard skeleton crafted from PETG was combined with shape memory alloy wires and extension springs to create a biomimetic structure that operates similar to the human hand, capable of gripping a wide range of objects. Relevant simulations were performed and discussed, the iterative fabrication process used to create each component …
Initial Orbit Determination Of Uncooperative Satellites Using Particle Swarm Optimization From The Point Of View Of A Novel Observer Orbit, Taylor Yow
Doctoral Dissertations and Master's Theses
Initial orbit determination is an incredibly valuable tool in the field of space situational awareness (SSA). As the number of launches increases every year, more objects are being put into space around the Earth and with political tensions mounting between certain space-accessing countries such as the United States of America (USA), Russia, and China, the number of satellites whose orbits are unknown to a political rival are increasing as well. In this research, orbit estimation of uncooperative target satellites from the point of view of novel orbits using particle swarm optimization (PSO) algorithm is explored. Two cost functions for the …
Benchmarking Of A Sco2 Heat Exchanger Flow Loop, David Velasco
Benchmarking Of A Sco2 Heat Exchanger Flow Loop, David Velasco
Doctoral Dissertations and Master's Theses
Heat transfer of supercritical carbon dioxide (sCO2) was studied experimentally by commissioning a sCO2 flow loop featuring a horizontal tube-in-tube counterflow heat exchanger with a circular cross section. The main objective was to establish experimental heat transfer research capabilities for sCO2 at Embry-Riddle Aeronautical University’s (ERAU) Thermal Science Lab. sCO2 experiences a drastic change in thermophysical properties near its critical point that results in unique heat transfer characteristics. The high pressures at which sCO2 exists make the large gradients in thermophysical and transport properties difficult to study, experimentally and numerically. However, understanding the heat transfer characteristics and thermophysical behavior of …
Development Of On-The-Fly Quasi-Steady State Approximation For Chemical Kinetics In Cfd, Abhinav Balamurugan
Development Of On-The-Fly Quasi-Steady State Approximation For Chemical Kinetics In Cfd, Abhinav Balamurugan
Doctoral Dissertations and Master's Theses
This study analyzes the feasibility of On-The-Fly Quasi-Steady-State Approximation (OTF-QSSA) application for solving chemical kinetics within Computational Fluid Dynamics (CFD) simulations, aiming to reduce the computational demand of detailed mechanisms. An algorithm that dynamically identifies and designates Quasi-Steady-State (QSS) species at specific grid locations and instances during the simulation was developed. With this information, our method pseudo-delays the advancement of concentrations for these QSS species—effectively setting their rate of concentration change to zero for a set number iteration before updating using the detailed mechanism and thereby omitting the computationally intensive processes typically required for their calculation during those skipped iteration. …
Damage Control Measures In Composites: Focus On Damage Tolerance Of Aerospace Structures, Kais Jribi
Damage Control Measures In Composites: Focus On Damage Tolerance Of Aerospace Structures, Kais Jribi
Doctoral Dissertations and Master's Theses
Barely Visible Impact Damage (BVID) in composite materials presents a stealthy yet significant risk to structural integrity, particularly challenging due to its elusive nature. The approach adopted here diverges from traditional methodologies, focusing on the novel application of Digital Image Correlation (DIC) to map surface area changes during in-situ Compression After Impact (CAI) tests. This technique allows for an in-depth analysis of planar strains along the x and y axes, shedding light on the material's behavior under stress.
A pivotal advancement lies in developing a method for precisely identifying when BVID-induced delamination recommences. By meticulously analyzing strain pattern deviations along …
Adaptive Control Of An Aeroelastic System For Active Flutter Suppression And Disturbance Rejection, Patrick Sterling Downs
Adaptive Control Of An Aeroelastic System For Active Flutter Suppression And Disturbance Rejection, Patrick Sterling Downs
Doctoral Dissertations and Master's Theses
The future of aircraft design strives for lighter weight, more aerodynamically efficient structures. These improvements may come with the drawback of increased structural flexibility and elevated aeroelastic effects, often resulting in a lower flutter speed. This motivates the implementation of advanced control methods to control aeroelastic systems over a range of flight conditions, suppress and delay the onset of flutter, and compensate for disturbances, actuator dynamics, and unmodeled nonlinear dynamics.
This dissertation first develops a novel method for constructing time-domain simulation models of two and three-dimensional aeroelastic systems, resulting in models that are suitable for the implementation of state-space control …
State Omniscience For Cooperative Local Catalog Maintenance Of Close Proximity Satellite Systems, Chris Hays
State Omniscience For Cooperative Local Catalog Maintenance Of Close Proximity Satellite Systems, Chris Hays
Doctoral Dissertations and Master's Theses
Resiliency in multi-agent system navigation is reliant on the inherent ability of the system to withstand, overcome, or recover from adverse conditions and disturbances. In large part, resiliency is achieved through reducing the impact of critical failure points to the success and/or performance of the system. In this view, decentralized multi-agent architectures have become an attractive solution for multi-agent navigation, but decentralized architectures place the burden of information acquisition directly on the agents themselves. In fact, the design of distributed estimators has been a growing interest to enable complex multi-sensor/multi-agent tasks. In such scenarios, it is important that each local …
A Comparison Of Beamforming Characteristics In Isotropic And Composite Plate Structures For Use In Structural Health Monitoring, Sarah Ketchersid
A Comparison Of Beamforming Characteristics In Isotropic And Composite Plate Structures For Use In Structural Health Monitoring, Sarah Ketchersid
Doctoral Dissertations and Master's Theses
Structural health monitoring in plate-like simple structures using phased array beamsteering of guided Lamb waves is useful in damage detection and evaluation efforts. Lamb waves can be effectively used for beamsteering using a linear array. The experimentation primarily focuses on beamsteering in the aluminum panel, which involves developing a simulation based on extracted data to visualize the dispersion of waves across the panel. By evaluating parameters such as slowness, velocity, and amplitude direction and variation for a specific metallic plate, the wavefront generated by a single wave source can be represented as a function of propagation angle and distance from …