Aerospace Engineering Commons^™

Towards Reduced-Order Model Accelerated Optimization For Aerodynamic Design, Andrew L. Kaminsky

Doctoral Dissertations

The adoption of mathematically formal simulation-based optimization approaches within aerodynamic design depends upon a delicate balance of affordability and accessibility. Techniques are needed to accelerate the simulation-based optimization process, but they must remain approachable enough for the implementation time to not eliminate the cost savings or act as a barrier to adoption.

This dissertation introduces a reduced-order model technique for accelerating fixed-point iterative solvers (e.g. such as those employed to solve primal equations, sensitivity equations, design equations, and their combination). The reduced-order model-based acceleration technique collects snapshots of early iteration (pre-convergent) solutions and residuals and then uses them to project …

Development And Implementation Of A Novel Resonantly Ionized Photoemission Thermometry Technique For One-Dimensional Measurements, Walker B. Mccord

Doctoral Dissertations

In this work, Resonantly Ionized Photoemission Thermometry (RIPT) is established and validated as a novel, non-intrusive, non-seeded, One-Dimensional (1D) line thermometry technique. The RIPT technique resonantly ionizes a target molecule via REMPI (Resonant Enhanced Multi-Photon Ionization) of selectively chosen rotational peaks within a resonant absorption band. Thus, efficiently ionizing and subsequently exciting local nitrogen molecules either by direct or indirect schemes. The excited nitrogen deexcites through photoemissions of the first negative band of N₂⁺[molecular nitrogen], specifically near 390, 425, and 430nm [nanometers], that is then acquired as a 1D line signal. The signal strength at all transitions …

Feasibility Study Of Slotted, Natural-Laminar-Flow Airfoils For High-Lift Applications, Hector David Ortiz Melendez

Doctoral Dissertations

A computational fluid dynamics approach to evaluate the feasibility of a slotted, natural-laminar-flow airfoil designed for transonic applications, to perform as a high-lift system was developed. Reynolds-Averaged Navier-Stokes equations with a laminar-turbulent transition model for subsonic flow at representative flight conditions were used for this analysis. Baseline high-lift simulations were performed to understand the stall characteristics of the slotted, natural-laminar-flow airfoil. Maximum aerodynamic efficiency was observed with a constant slot-width. In addition, the effectiveness of the aft-element as a high-lift device was explored. Results indicate that a micro-flap is a viable option as a lift effector. These are most effective …

Fabrication, Thermophysical, And Mechanical Properties Of Cermet And Cercer Fuel Composites For Nuclear Thermal Propulsion, Neal D. Gaffin

Doctoral Dissertations

Nuclear thermal propulsion (NTP) utilizes nuclear fission to double the efficiency of
in-space propulsion systems compared with traditional combustion rocket systems.
NTP systems are limited primarily by the fuel material choice, due to the extreme
conditions they will need to endure, including temperatures up to 3000 K, multiple
thermal cycles with rapid heating and cooling, exposure to hot flowing hydrogen,
large thermal gradients, and high neutron flux. Particle based fuels, namely ceramic-
metallic (cermet) and ceramic-ceramic (cercer) composites are both promising fuel
element material candidates for NTP. Given the high temperature nature, these
materials are difficult to fabricate and very …

Predictive Capabilities Of Laminar-Turbulent Transition Models For Aerodynamics Applications, Jared Alexander Carnes

Doctoral Dissertations

Laminar-turbulent boundary-layer transition has a demonstrable impact on the performance of aerospace vehicles. The ability to accurately predict transition is integral to properly capturing relevant flow physics. Traditionally, computational fluid dynamics simulations are performed fully turbulent, meaning that laminar flow is neglected. This, however, can result in errant predictions of vehicle performance as quantities such as skin-friction drag may be overpredicted. Resultingly, development of Reynolds-averaged Navier-Stokes transition models has seen significant attention over the last decades in order to model transition and realize the performance improvements of laminar flow.

In this work, the behaviors of several different transition-prediction methods are …

Upscaling And Development Of Linear Array Focused Laser Differential Interferometry For Simultaneous 1d Velocimetry And Spectral Profiling In High-Speed Flows, Kirk Davenport

Masters Theses

In this research a new configuration of linear array-focused laser differential interferometry (LA-FLDI) is described. This measurement expands on previous implementations of LA-FLDI through the use of an additional Wollaston prism. This additional prism expands the typical single LA-FLDI column into two columns of FLDI point pairs. The additional column of probed locations allows for increased spatial sampling of frequency spectra as well as the addition of simultaneous wall normal velocimetry measurements. The new configuration is used to measure the velocity profile and frequency content across a Mach 2 turbulent boundary layer at six wall normal locations simultaneously. Features of …

Analysis Of Turbulent Flow Behavior In Helicopter Rotor Hub Wakes, Forrest Mobley

Masters Theses

The rotor hub is one of the most important features of all helicopters, as it provides the pilot a means for controlling the vehicle by changing the characteristics of the main and tail rotors. The hub also provides a structural foundation for the rotors and allows for the rotor blades to respond to aerodynamic forces while maintaining controllability and stability. Due to the inherent geometry and high rate of rotation, the rotor hub in its current form acts a large bluff body and is the primary source of parasite drag on the helicopter, despite its relatively small size. The rotor …

Nuclear Thermal Rocket Engine Control Autonomy Via Embedded Decision, David Sikorski

Doctoral Dissertations

This doctoral dissertation presents an investigation of embedded decision capabilities as a means for developing nuclear reactor autonomous control. Nuclear thermal propulsion (NTP) is identified as a high priority technology for development, and is the focus of this research. First, a background investigation is presented on the state of the art in nuclear thermal rocket (NTR) engine control and modeling practices, resulting in the development of a low order NTR engine dynamic model based on the literature. The engine model was used to perform the following investigation, and is intended to serve as a research platform for the future development …

Experimental Investigation Of Supersonic Jets Using Optical Diagnostics, Theron James Price

Doctoral Dissertations

The complexity of many fluid flows and phenomena is a well-known characteristic driven primarily by turbulence, which has been a focal point of study for decades. Most engineering applications in fluids will encounter turbulence, and hence the need to understand how turbulence might influence the problem at hand is omnipresent. In many turbulent flows, there are large-scale coherent structures which directly influence macro-scale processes of engineering relevance, such as noise production. Over decades of study, it has been demonstrated that similar structures are often observed across many flowfields, despite differences in characteristic parameters, and this has led to the pursuit …

Path Planning And Flight Control Of Drones For Autonomous Pollination, Chapel R. Rice

Masters Theses

The decline of natural pollinators necessitates the development of novel pollination technologies. In this thesis, a drone-enabled autonomous pollination system (APS) that consists of five primary modules: environment sensing, flower perception, path planning, flight control, and pollination mechanisms is proposed. These modules are highly dependent upon each other, with each module relying on inputs from the other modules. This thesis focuses on approaches to the path planning and flight control modules. Flower perception is briefly demonstrated developing a map of flowers using results from previous work. With that map of flowers, APS path planning is defined as a variant of …

Pscc Formula Sae Aerodynamic Sub-Team, Nicholas Boccuzzi, Candler Boland, Adam Cain, Michael Palmaccio, Anna "Liece" Tessman

Chancellor’s Honors Program Projects

No abstract provided.

A Numerical Optimization Study Of A Novel Electrospray Emitter Design, Joshua H. Howell

Masters Theses

The low thrust and high specific impulse of electric propulsion has been brought to the forefront for CubeSat and small spacecraft applications. Electrospray thrusters, which operate via electrostatic principles, have seen much research, development, and application in recent years. The small sizes of the spacecraft that utilize electrospray thrusters has focused development into the miniaturization of this technology to the micro-scale. Miniaturization introduces design challenges that must be addressed, including power supply mass and footprint requirements. This consequence requires investigation into the effects of design choices on the thruster onset voltage, defined as the voltage at which ion emission begins. …

Quasi-One-Dimensional Flow Method For Nuclear Thermal Propulsion Simulator Design, Ethan M. Long

Masters Theses

Quasi-One-Dimensional flow methods are commonly used to solve flow situations that have multiple driving influences, i.e. heat transfer, area change, and friction. They hold advantages over other computational fluid dynamics methods due to their much lower computational costs and overall simplicity. Typically, these methods are limited in their ability to solve flows due to the simplifying assumptions used. In this model, a simple heat transfer calculation is combined with NASA’s Chemical Equilibrium with Applications to constantly update chemical properties within the simulation. In this thesis, a quasi-one-dimensional model including these additions is developed and applied to a NTP simulator design …