Engineering Commons^™

Development And Flight Test Of Moving-Mass Actuated Unmanned Aerial Vehicle, Sampath Reddy Vengate

Mechanical and Aerospace Engineering Theses - Archive

Conventional airplane control is achieved by aerodynamic control surfaces by generating moments around all the three axes of the aircraft. Defections of the control surfaces have some disadvantages such as induced drag, increase in radar signature, and exposure to high temperature in high speed applications. As an alternative moment generation mechanism, prior research proposed internal mass-actuation, which is to generate gravitational moment by changing the center of gravity of the aircraft through motion of internal masses within the aircraft. Prior research investigated the feasibility and benefit of internal mass-actuation in airplane control based on simulation analysis. The main focus of …

Numerical Studies On Spin Coating Of Metals, Varun Nanjunda Rao Viswamithra

Mechanical and Aerospace Engineering Theses - Archive

Spin coating is a surface coating process which involves spreading a liquid dispensed on the center of a rotating substrate. The liquid is discharged using a suitable method on to the substrate rotating at a constant angular speed. The spinning speed is controlled to obtain a coating of desired thickness with faster spinning resulting in thinner coating. The thickness of the coating also depends on the properties of the fluid and other process parameters. Centrifugal force is introduced into the code as radial component of acceleration. The first part of the code solves the continuity and the Navier-Stokes equations, with …

Cfd Analysis And Design Optimization Of Heat Sink For Oil Immersion Cooling, Koushik Epuri

Mechanical and Aerospace Engineering Theses - Archive

Air cooling is predominant cooling technique employed in most of the data centers. As the demand for High performance computing (HPC) which deploy large concentration of high-end servers (30 kW to 200 kW per rack) is increasing, it is becoming challenging to cool the systems using air cooling. Liquid cooling has significant advantages over air cooling techniques due to higher heat capacities of fluids. Liquid immersion cooling using dielectric and non-corrosive mineral oils is one of the potential alternative to air cooling methods for high density data centers. In this work, we consider a third generation open compute server optimized …

Design And Stiffness Optimization Of Quadri-Directional Composite Grid Lattice Structures, Gajendra Devanga Gangadara

Mechanical and Aerospace Engineering Theses - Archive

Composite grid structures are rib stiffeners connected to each other rigidly in a pattern or a lattice such that the whole grid pattern has certain smeared stiffness property and has a certain structural behavior. The main focus of this thesis is to design the geometric pattern of a Quadri-directional composite grid lattice such that it has the prescribed stiffness moduli. The research is divided into three phases, in the first phase, the equation for stiffness moduli, the reduced stiffness matrix [Q] and the laminate stiffness matrices [ABD] of the grid pattern is derived for Quadri-directional grid panels. In the second …

Flight Test Investigation On The Effects Of Aircraft Flap Configuration Change On Longitudinal Trim, Tiziano Bernard

Theses and Dissertations

Loss of Control (LOC) in general aviation has been a topic of extensive study and analysis in the United States and the European Union due to a long series of aircraft accidents in the past decades. The National Transportation Safety Board (NTSB) has identified over 1500 accidents in the traffic pattern involving LOC in general aviation aircraft between 1982 and 2015. LOC has often been attributed to deficiencies in pilot training, and the typical recommendation to reduce the number of accidents is to provide further training in stalls and spins. The European Aviation Safety Agency (EASA) has performed research that …

Experimental, Numerical, And Analytical Slosh Dynamics Of Water And Liquid Nitrogen In A Spherical Tank, Jedediah Morse Storey

Theses and Dissertations

Understanding, predicting, and controlling fluid slosh dynamics is critical to safety and improving performance of space missions when a significant percentage of the spacecraft’s mass is a liquid. Computational fluid dynamics simulations can be used to predict the dynamics of slosh, but these programs require extensive validation. Many experimental and numerical studies of water slosh have been conducted. However, slosh data for cryogenic liquids is lacking. Water and cryogenic liquid nitrogen are used in various ground-based tests with a spherical tank to characterize damping, slosh mode frequencies, and slosh forces. A single ring baffle is installed in the tank for …

Safte-Vat Functionality Effects On Flight Instructors' Situation Awareness And Instrument Student Pilots' Performance During Ftd Training, Rafael E. Abreu Vega

Doctoral Dissertations and Master's Theses

SAFTE-VAT is a virtual air traffic control systems that adds the capability to integrate automated air traffic control functionality and generate semiautonomous and autonomous air traffic to the Frasca 172S level 6 plus FTD to improve behavioral fidelity and to facilitate flight instructors the capacity to focus more on instructing student pilots instead of role-playing ATC duties. While SAFTE-VAT may offer a more realistic ATC interaction experience onboard the FTD that may result in a positive transfer of training increase, the effects on flight instructors’ situation awareness and overall student pilot performance are uncertain. In this small study, flight instructors …

An Experimental Study Of Momentum-Driven Unsteady Jets, Sravan Kumar Artham

Doctoral Dissertations and Master's Theses

Jets are seen commonly in nature and engineering and can be broadly classified into steady and unsteady jets. The study of unsteady jets has received little attention when compared to its steady counterpart. A type of unsteady jet is the turbulent puff which is a momentum driven jet in which fluid is ejected from a jet orifice intermittently. Common examples of turbulent puff like jets are coughs and volcanoes. The studies on momentum driven unsteady jets have primarily focused on single ejection events (single puffs) where an instantaneous supply of momentum drives the source fluid downstream of a nozzle. This …

Computational Investigation Of Impingement Cooling For Regeneratively Cooled Rocket Nozzles, Bianca A. De Angelo

Doctoral Dissertations and Master's Theses

Jet impingement cooling is an internal cooling configuration used in the thermal management of temperature sensitive systems. With rocket engine combustion temperatures rising as high as 3600 K, it is essential for a cooling method to be applied to ensure that the nozzle integrity can be maintained. Therefore, a novel heat transfer study is conducted to investigate if jet impingement cooling is feasible for a regenerative cooling rocket nozzle application. Regenerative cooling for liquid propellant rockets has been widely studied. However, to the best of the author’s knowledge, there is currently no literature describing this method in conjunction with impingement …

Investigation Of Pin Fin Cooling Channels For Applications In Gas Turbines, Royce Fernandes

Doctoral Dissertations and Master's Theses

Gas turbine blades are often cooled using internal cooling channels to prevent failure at temperatures beyond material limitations. Pin fin channels are commonly used on the trailing edge of the blades, where they enhance heat transfer and also provide structural support. This study focuses on the validation of several commercially available RANS turbulence models in CFD, that are used to computationally simulate the flow features inside a pin fin cooling channel. Turbulence models investigates are: Menter’s kω SST, realizable k-ε, and a quadratic formulation of the realizable k-ε model. The geometry investigated is a staggered 8 row pin fin channel. …

The Effect Of Axial Spacing Of Constant And Variable Blockages On The Deflagration-To-Detonation Transition In A Pulse Detonation Engine, Nicole Gagnon

Doctoral Dissertations and Master's Theses

An investigation was conducted into the effects of obstacle spacing on the deflagration-to-detonation transition section length in a pulse detonation engine. Testing was conducted with one hundred and ninety-five different obstacle, and spacing configurations. The configurations included constant, as well as variable spacing between obstacles. The goal of this investigation was to correlate the spacing between obstacles and the blockage ratio of the obstacles with the detonation success and the shortening of the DDT section. The ten cases that achieved the highest percentage of detonations were investigated further to determine the distance needed for the deflagration-to-detonation transition. A 33% blockage …

Optical Tracking And Spectral Characterization Of Cubesats For Operational Missions, Forrest Gasdia

Doctoral Dissertations and Master's Theses

Orbital debris in low Earth orbit is of growing concern to operational satellites from the government and commercial sector. With an uptick in worldwide satellite launches and the growing adoption of the CubeSat standard, the number of small objects in orbit are increasing at a faster pace than ever. As a result, a cascading collision event seems inevitable in the near future.

The United States Strategic Command tracks and determines the orbit of resident space objects using a worldwide network of radar and optical sensors. However, in order to better protect space assets, there has been increased interest in not …

Vibration Analysis Of A Composite Wing Box With Arbitrarily Shaped Spars And Ribs, Rossana R. Fernandes

Doctoral Dissertations and Master's Theses

In this research, the free vibration analysis of composite wing boxes with curvilinear spars and ribs is performed. Modern manufacturing technologies, such as Electron Beam Freeform Fabrication and Friction Stir Welding, have allowed the manufacturing of arbitrarily shaped stiffeners. Curvilinear stiffeners provide flexibility in design as they can assume an infinite number of paths. Curvilinear spars and ribs can in some instances provide a better vibration and static response than their straight counterparts while reducing the overall mass of the structure. An equivalent continuum plate model of a wing box using energy formulations is proposed at the preliminary design stage …

An Experimental Study Of Synthetic Jet Actuators With Application In Airfoil Lco Control, Sanjay Krishnappa

Doctoral Dissertations and Master's Theses

An experimental study on the development and implementation of Synthetic Jet Actuators (SJAs) is conducted for eliminating aeroelastic phenomenon such as Limit Cycle Oscillations (LCO). One of the biggest challenges involved in the design of UAVs operating in unsteady atmosphere conditions is the susceptibility of the airframe to aeroelastic instabilities, such as flutter or LCO. Suppression of such instabilities can be achieved through the implementation of Active Flow Control (AFC) techniques, however to this day, a limited amount of experimental studies exist. Thus, the focus of this work is to develop a new AFC method consisting of an actuator that …

Mechanical And Electrical Characterization Of Hybrid Carbon Nanotube Sheet-Graphene Nanocomposites For Sensing Applications, Jiukun Li

Doctoral Dissertations and Master's Theses

The unique mechanical and electrical properties of carbon nanotubes and graphitic structures have drawn extensive attention from researchers over the past two decades. The electro-mechanical behavior of these structures and their composites, in which electrical resistance changes when mechanical deformation is applied facilitates their use in sensing applications.

In this work, carbon nanotube sheet- epoxy nanocomposites with the matrix modified with various contents of coarse and fine graphene nanoplatelets are fabricated. The addition of a secondary filler results in improvements of both electrical and mechanical properties. In addition, with the inclusion of the second filler, change in resistivity with mechanical …

Fluidic Jet Turbulence Generators For Deflagration To Detonation Transition In Pulsed Detonation Combustors, Jarrett E. Lowe

Doctoral Dissertations and Master's Theses

The goal of this study is to establish the dominant flow structure required to effectively accelerate the turbulent deflagration flame front to detonation velocity in the shortest possible distance while using a single Jet in Cross Flow (JICF). Jets in crossflow, depending on orientation and momentum ratio, can induce two types of flow structures that propagate downstream; vortex filaments and turbulent eddies. Vortex flow structures are coherent rotating columns that can persist for a considerable distance before diffusing. Turbulent eddies are characterized as random fluctuations in flow velocity or small pockets of rotation. The test rig used for this study …

Magneto-Rheological Fluid Device As Artificial Feel Force System On Aircraft Control Stick, Vignesh Manoharan

Doctoral Dissertations and Master's Theses

The conventional feel system in any aircraft occupies large space in the cockpit and has complicated designs. The primary objective of this research is to develop an artificial feel force system that can overcome some drawbacks of the current feel force system. A novel feel system using magneto-rheological (MR) fluid is constructed to precisely control the shear stress under the magnetic field. To validate the functionality of the MR artificial feel system, the final system is fabricated and multiple tests are performed to acquire force-velocity characteristics that are compared to the mathematical model derived. In addition, the reference model of …

Study Of Hybrid Magneto-Active Propellant Management Device For Slosh Damping, Leander Paul

Doctoral Dissertations and Master's Theses

Sloshing of liquid upon the application of an external force is a natural phenomenon as the free surface is allowed to move without any constraints. Study of slosh is an ongoing research for many decades and many novel inventions in Propellant Management Devices (PMDs) such as the rigid baffles and elastomeric membranes have been implemented to counteract the free surface effect in both passive and active membrane known as Magneto-Active Propellant Management Device (MAPMD) to actively control the free surface effect and reduce fuel slosh is explored in this research. Being a hybrid membrane, it would initially offer passive resistance …

2d Aeroacoustic Analysis Of Flow In The Flame Trench, Meghan Pokorski

Doctoral Dissertations and Master's Theses

We present here a methodology for using the commercial software ANSYSFLUENT to predict the acoustic field associated with Space-Launch System (SLS). We consider a two-dimensional model of flame deflector, and flame trench. The ANSYS code is then used to simulate the internal flow. Both the steady state case is considered along with other cases where the inflow has a harmonic component. A Ffowcs-Williams Hawking (FWH) surface is then constructed within the computational domain to use the computed flow fluctuations to obtain the acoustic field. The acoustic data was then compared to the experimental data.

When using the ANSYS code for …

Analysis Of A Coupled Micro- And Triple-Impingement Cooling Configuration In The C3x Vane, Chase D. Rossman

Doctoral Dissertations and Master's Theses

This study attempts to improve the trailing edge protection of a turbine vane by incorporating two concepts from the literature. These two concepts are optimized near wall cooling passages and a triple-impingement configuration in the vane trailing edge. Finally this study explores a CFD conjugate analysis based on the Shear Stress Transport k(l) turbulence model. The overall goal is to produce a more effective cooling configuration by studying the effects of the flow and heat transfer of the dual configuration, while keeping the integrity of the turbine vane. Star-CCM+ was utilized to carry out the computational data on a 3-D …

Prediction Of Tonal Acoustic Radiation Due To Feedback-Loop Resonant Interactions In Transitional Airfoils, Seyyed Saman Salehian

Doctoral Dissertations and Master's Theses

The objective to this work is to employ the surface integral methods to study the far-field noise propagation from the flow acoustic resonant interactions of the transitional airfoil. The Potential-Theoretic Method (PTM) as an advancement to traditional Kirchhoff methods is presented. The PTM eliminated the need to calculate the normal derivatives of pressure and an arbitrary Kirchhoff surface can be employed. The numerical procedure to implement the PTM is fairly simple. The formulation and physical assumptions of the approach is reviewed, and the numerical procedure is implemented. Furthermore, the two dimensional formulation of the Ffowcs Williams - Hawkings (FW-H) equation …

Benchmark Experiments For Natural Convection In Nuclear Fuel Rod Bundles, Kyle L. Jones

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Buoyancy is the mechanism through which heated air causes fluid motion due to a difference in temperature between a body and the surrounding fluid. This fluid motion can be very erratic and unstable, which creates a difficult problem when attempting to simulate this fluid motion. Using high performance computational power the capability of simulating these complex interactions is available but requires assessment to determine the accuracy of these difficult flow scenarios. This study provides experimental data that can be used to assess the simulation’s accuracy and to ensure the computational models are achieving the correct solution. The Rotatable Buoyancy Tunnel …

Microalgae Sorption Of Ten Individual Heavy Metals And Their Effects On Growth And Lipid Accumulation, Eric M. Torres

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The purpose of this study is to determine the potential microalgae have for being a heavy metal remediation tool. Heavy metals are naturally occurring elements that can be found inside the earth or on its surface. Typically, heavy metals are found naturally at low concentrations. However, through human activities, heavy metals are continually making their way to the surface and being concentrated. This happens largely through mining and manufacturing operations. For example, NiCd batteries produce waste containing nickel and cadmium, and paper manufacturing produces waste containing high levels of lead. As underdeveloped nations continue to industrialize and the world population …

Investigating The Effect Of Capping Layers On Final Thin Film Morphology After A Dewetting Process, Benjamin C. White

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Nanoparticles on a substrate have numerous applications in nanotechnology, from enhancements to solar cell efficiency to improvements in carbon nanotube growth. Producing nanoparticles in a cheap fashion with some control over size and spacing is difficult to do, but desired. This work presents a novel method for altering the size and spacing of nickel and gold nanoparticles. Dewetting is a methodology to reduce thin films to an ensemble of discrete droplets. The introduction of alumina capping layers to thin nickel films during a pulsed laser-induced dewetting process has yielded reductions in the mean and standard deviation of radii and pitch …

Path Following By A Quadrotor Using Virtual Target Pursuit Guidance, Abhishek Manjunath

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Missile guidance laws have been solely developed to follow and intercept a target thereby destroying or damaging it. In this research, the primary objective is to modify and adopt a missile guidance law to be used on a quadrotor to follow a virtual target. The target is termed 'virtual' as it only exists mathematically in the form of equations. The goal is to have the quadrotor successfully following the predefined path (described by the target) while maintaining a fixed distance from the virtual target. To ensure viability and assess performance, a detailed comparison with another path following law is made.

Quadrotor Uav Path Following Using Trajectory Shaping, Parwinder Singh Mehrok

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The propose of this research is to develop a path following control law known as Trajectory Shaping. The approach is to develop a three- dimensional (3D) version of it from an existing two-dimensional (2D) model. Apart from research on this 3D control law, a multirotor unmanned aerial vehicle (UAV) platform, having four rotors and known as quadrotor is designed from the ground up for validating the concept of path following. Several pre-defined paths like the circle and figure-eight trajectories are used to apply the newly developed version of this control law. The existing 2D concept of Trajectory Shaping guidance …

Throttleable Gox/Abs Launch Assist Hybrid Rocket Motor For Small Scale Air Launch Platform, Zachary S. Spurrier

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The ability for an aircraft-based launch platform to place an orbital payload onto a nominal launch trajectory at a higher energy state -- altitude, velocity, flight path angle, and azimuth --using highly-efficient air breathing propulsion instead of a much lower-efficiency rocket system, offers the potential for a significantly smaller launch vehicle. An airborne platform also provides the ability to launch from multiple locations and allows for significantly increased "system responsiveness." The NASA Armstrong Flight Research Center’s Towed Glider Air-Launch System (TGALS) is a small-scale flight research project investigating the feasibility for a remotely-piloted, towed, glider system to act as a …

Effects Of Radiation Heating On Additively Printed Hybrid Fuel Grain Oxidizer-To-Fuel Ratio Shift, Stephen L. Merkley

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This thesis examined the hypothesis that radiative heat transfer in small-scale printed-fuel hybrid rocket motors is responsible for the observed decreasing oxidizer-to-fuel (O/F) ratio shift. The magnitude of the radiation term was negligible for the motor sizes and types of propellants that have been previously tested, but was reintroduced in this study. To prove this hypothesis, a detailed enthalpy balance model was developed and tested using experimental fuel regression rate data obtained from a variety of motor scales using additively-manufactured acrylonitrile butadiene styrene (ABS) fuel grains.

Impact Of Mass And Bond Energy Difference And Interface Defects On Thermal Boundary Conductance, Changjin Choi

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Many portions of energy generated in the U.S. are not used and take the form of wasted heat due to a poor heat transfer efficiency. This fact leads research communities to focus on thermoelectrics as a means for using waste heat through direct thermal to electrical energy conversion. One way to enhance thermoelectric efficiency is to reduce thermal conductivity through nanostructuring. In nanostructures, understanding energy transport across the interface of two materials is important because interfaces dominate the resistance to overall thermal transport of the system and can be described by thermal boundary conductance (TBC). Also of note, an understanding …

Development Of A Three-Dimensional High-Order Strand-Grids Approach, Oisin Tong

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The strand-Cartesian grid approach is a unique method of generating and computing fluid dynamic simulations. The strand-Cartesian approach provides highly desirable qualities of fully-automatic grid generation and high accuracy. This work focuses on development of a high-accuracy methodology (high-order scheme) on strand grids for two and three dimensions.

In this work, the high-order scheme is extended to high-Reynolds number computations in both two and three dimensions with the Spalart-Allmaras turbulence model and the Menter SST turbulence model. In addition, a simple limiter is explored to allow the high-order scheme to accurately predict discontinuous flows.

Extensive verification and validation is conducted …