Aerospace Engineering Commons^™

Multiphase Flow Modeling And Analysis Of Filling Process For Pulsed Detonation Engines, Swati Chandran Thirumangalath

Mechanical and Aerospace Engineering Theses - Archive

The filling process of a pulsed detonation engine with fuel and oxidizer should be carried out quickly in order to maintain a high frequency of operation. The objectives of this research were to model an efficient inlet system for filling the detonation tube with fuel/air mixture in stoichiometric ratio and to evaluate various filling schemes. Numerical modeling of the filling process was done using PointwiseTM for meshing and FluentTM as the flow solver, solving the Reynolds-averaged Navier-Stokes equations with a k-? turbulence model. Five different filling configurations were studied, including endwall, normal and angled, opposing and staggered sidewall. The fuel …

A Comparative Study On Micro Electro-Discharge Machining Of Titanium Alloy (Ti-6al-4v) And Shape Memory Alloy (Ni-Ti), Pegah Kakavand

Masters Theses & Specialist Projects

The purpose of this research was to investigate the surface modifications that take place during the machining of NiTi SMA and Ti-6Al-4V with micro-EDM. This was done by creating an array of blind holes and micro-patterns on both work-pieces. To analyze the machined surface and investigate the results, scanning electron microscope (SEM), energy dispersive X- ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques were employed. In addition, the effects of various operating parameters on the machining performance was studied to identify the optimum parameters for micro-EDM of NiTi SMA and Ti-6Al-4V. Recently, aerospace and biomedical industries have placed a high …

Modeling Of Environmentally Assisted Fatigue Crack Growth Behavior, Sree Phani Chandar Reddy

Dissertations

The formation of fatigue cracks and their propagation due to cyclic loading in metals have been a concern for more than hundred years. Since fatigue failure were first reported by the railroad industry in 1840s, tremendous progress has been achieved in understanding fatigue behavior of metals. But fatigue damage is still a concern due to its complex dependency on various environmental variable like humidity, temperature, time and corrosive environment. Although numerous theories and models have been proposed in the past, the effects of environment on fatigue crack growth (FCG) is not completely understood. This dissertation aims to shed light on …

Simulation Of A Dissimilar Fresnel Relfectarray Antenna, Paul L. Rogers

Electrical Engineering Undergraduate Honors Theses

Planar reflectarray antennas behave similarly to parabolic dish antennas, but are flat in their construction. They work by having areas on the planar surface of different reflection phase, causing the signal to be reflected to a focal point. This is done today by making planar patch antennas with the required reflection phase. These antennas are typically used in aerospace. This paper specifically discusses a planar reflectarray antenna that was originally constructed in Millimeter Wave Circularly Polarized Fresnel Reflector for On-Board Radar on Rescue Helicopters by K. Mazouni. In this paper, the authors eight different shaped antennas to form the planar …

Simulations Of Nanoscale Ni/Al Multilayer Foils With Intermediate Ni2al3 Growth, I. E. Gunduz, S. Onel, C. C. Doumanidis, C. Rebholz, Steven F. Son

Purdue Energetics Research Center Articles

Nanoscale multilayers of binary metallic systems, such as nickel/aluminum, exhibit self-propagating exothermic reactions due to the high formation enthalpy of the intermetallic compounds. Most of the previous modelingapproaches on the reactions of this system rely on the use of mass diffusionwith a phenomenological derived diffusion coefficient representing single-phase (NiAl) growth, coupled with heat transport. We show that the reaction kinetics, temperatures, and thermal front width can be reproduced more satisfactorily with the sequential growth of Ni2Al3 followed by NiAl, utilizing independently obtained interdiffusivities. The computational domain was meshed with a dynamically generated bi-modal grid consisting of fine and coarse zones …

Synthetic Aperture Radar: Rapid Detection Of Target Motion In Matlab, Daniel S. Kassen

Master's Theses

Synthetic Aperture Radar (SAR) has come into widespread use in several civilian and military applications. The focus of this paper is the military application of imaging point targets captured by an airborne SAR platform. Using the traditional SAR method of determining target motion by analyzing the difference between subsequent images takes a relatively large amount of processing resources. Using methods in this thesis, target motion can be estimated before even a single image is obtained, reducing the amount of time and power used by a significantly large amount. This thesis builds on work done by Brain Zaharri and David So. …

Experimental Investigation Of Drag Reduction By Trailing Edge Tabs On A Square Based Bluff Body In Ground Effect, Scott R. Sawyer

Master's Theses

This thesis presents an experimental investigation of drag reduction devices on a bluff body in ground effect. It has previously been shown that the addition of end-plate tabs to a rectangular based bluff body with an aspect ratio of 4 is effective in eliminating vortex shedding and reducing drag for low Reynolds number flows. In the present study a square based bluff body, both with and without tabs, will be tested under the same conditions, except this time operating within proximity to a ground plane in order to mimic the properties of bounded aerodynamics that would be present for a …

Supersonic Retro-Propulsion Computational Fluid Dynamics Analysis Applied To Future Mars Mission, Margarita Nataly Brandt

Doctoral Dissertations and Master's Theses

Supersonic Retro-Propulsion is one of the most promising emerging technologies being considered by NASA for use in future Mars missions. This new form of Entry Descent Landing has the potential to help increase the allowable payload mass currently constraining many science instruments and operations. Computational Fluid Dynamics was used to show the feasibility of supersonic retro - propulsion in Mars atmospheric conditions. The results presented show the SRP will be able to perform satisfactory using the same conditions that the Curiosity Rover was exposed to during its landing sequence. The plume expansion was analyzed for various cases, moving from free …

Aerodynamic And Structural Design Of A Winglet For Enhanced Performance Of A Business Jet, Nicolas El Haddad

Doctoral Dissertations and Master's Theses

The preliminary design of a winglet to improve the range and fuel burn of the Falcon 10 business jet is presented. Twelve candidate geometries were studied varying the cant angle and the span. The configuration offering the best compromise between induced drag reduction, profile drag increase and weight increase due to the winglet structure and necessary wing structural reinforcement was selected. More refined analysis was performed for that winglet with Reynolds averaged Navier-Stokes computational fluid dynamics and finite element analysis. Range and fuel burn were finally calculated for a typical mission using these refined results. The selected winglet, with a …

Adaptive, Neural And Robust Control Of Wing-Rock And Aeroelastic System, Prince Ghorawat

UNLV Theses, Dissertations, Professional Papers, and Capstones

Modern aircraft exhibit wing-rock phenomenon and aeroelastic instability. Wingrock (roll single degree of freedom motion) and aeroelastic systems' (two degrees of freedom) behavior are described by complex nonlinear differential equations. The nonlinearities in the dynamics of these systems give rise to limit cycle oscillations beyond critical speed of aircraft. The onset of wing-rock and aeroelastic instability limits the performance of aircraft and can even lead to catastrophic consequences. Therefore, control of wing-rock motion and stabilization of aeroelastic systems are important. In the past, several studies have been made and experimental and analytical results have been obtained to explain the wing-rock …

Modeling And Simulation Of Radiation From Electronic Transitions In Hypersonic Atmospheric Reentry Flow, Curtis Scholz

Doctoral Dissertations and Master's Theses

A capability for higher accuracy heat transfer modeling in CFD for hypersonic re-entry flows, via inclusion of thermal radiation, is sought. With temperatures reaching tens of thousands of degrees, radiation is known to be significant to chemical reaction rates and thermal boundary layer development, hence surface heat transfer and thermal ablation both to the heat shield and the backshell region of re-entry vehicles. Two current NASA solicitations seek such an improved capability relative to the Mars and Earth entry problems, as uncertainty typically leads to overdesign and excess weight. The present research develops a first physics-based “building block,” which computes …

Attitude Determination & Control System Design And Implementation For A 6u Cubesat Proximity Operations Mission, Francisco J. Franquiz

Doctoral Dissertations and Master's Theses

The purpose of this work is to discuss the attitude determination and control system (ADCS) design process and implementation for a 12 kg, 6U (36.6 cm x 23.9 cm x 27.97 cm) CubeSat class nano-satellite. The design is based on the requirements and capabilities of the Application for Resident Space Object Proximity Analysis and IMAging (ARAPAIMA) proximity operations mission. The satellite is equipped with a cold gas propulsion system capable of exerting 2.5 mN m torques in both directions about each body axis. The attitude sensors include an angular rate gyro and star tracker (STR), supplemented by the payload optical …

Surface Structure And Its Effect On Reducing Drag, Ragini Ramachandran

Doctoral Dissertations and Master's Theses

A miniature subsonic open return wind tunnel was designed and fabricated to measure drag on small test models at low Reynolds numbers. The wind tunnel featured a sensitive strain gauge type load cell. The average drag coefficient of sphere and cube test models were used to validate the miniature wind tunnel, and the values obtained were consistent with published results over the range of Reynolds numbers tested. These initial results gave confidence that the tunnel could be used to study the effects of surface finish on the drag of various models. Several fabrics with differing ribbed surface structures, including a …

Phased Array Beamsteering In Composite Laminates For Guided Wave Structural Health Monitoring, Peter Osterc

Doctoral Dissertations and Master's Theses

In this study a guided wave phased array beamsteering approach is applied to composite laminates. Current beamsteering algorithms derived for isotropic materials assume omnidirectional wave propagation. Due to inherent anisotropy in composites, guided wave propagation varies with direction and wavefronts no longer have perfect circular shapes.

By examining slowness, velocity and wave curves, as well as amplitude variation with direction for a given composite laminate, the wavefront from a single source can be described as a function of the angle of propagation and distance from origin. Using this approach, a more general delay and sum beamforming algorithm for composite laminates …

Techno-Economic Feasibility And Life Cycle Assessment Of Dairy Effluent To Biofuel Via Hydrothermal Liquefaction, Hailey M. Summers

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Delactosed whey permeate (delac) is a low valued by-product in the dairy industry with 90 million tons annually disposed of worldwide. Upgrading delac to bioproducts, specifically biofuel, has been demonstrated at laboratory scale through yeast fermentation. However, the large-scale environmental impact and economic feasibility of this process is yet to be quantified. Further research, focused on evaluating the sustainability, scalability and economic feasibility of the fermentation pathway, directs research and development to move the technology towards commercialization. The enclosed research incorporates biological experimentation with engineering systems modeling to evaluate the large-scale environmental impacts and economic feasibility of generating bioproducts from …

Methods Of Processing Kenaf Chopped Strand Mats For Manufacturing Test Specimens And Composite Structures, Joshua W. Heil

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Every year in the United States, 10 to 11 million vehicles reach the end of their life cycle. Nearly all of these go to a recycling facility. After the recycling process is complete an average of 25% of each vehicle, by weight, goes to waste. This demonstrates the need to use natural fibers in parts that could be recycled, like parts that can be made from kenaf. There are many reasons to consider using natural/bio-fiber composites (bio-composites). These reasons include human health and environmental factors as well as advantages that natural fibers have over fiberglass, such as: lower costs and …

High Regression Rate Hybrid Rocket Fuel Grains With Helical Port Structures, Sean D. Walker

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Hybrid Rockets are popular in the aerospace industry due to their storage safety, simplicity, and controllability during rocket motor burn. However, they produce fuel regression rates typically 25% lower than solid fuel motors of the same thrust level. These lowered regression rates produce unacceptably high oxidizer-to-fuel (O/F) ratios that produce a potential for motor instability, nozzle erosion, and reduced motor duty cycles. To achieve O/F ratios that produce acceptable combustion charactersitics, traditional cylindrical fuel ports are fabricated with very long length-to-diameter ratios to increase the total burning area. these high aspect ratios produce further reduced fuel regression rate and trust …

Parameterized Least-Squares Attitude History Estimation And Magnetic Field Observations Of The Auroral Spatial Structures Probe, Ryan J. Martineau

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

As charged particles from the Sun enter the Earth’s atmosphere and create the aurora borealis (Northern lights) and aurora australis (Southern lights), energy is transferred to the atmosphere. In order to better understand the energy transfer processes, the Auroral Spatial Structures Probe rocket was launched to make measurements in the active aurora. Several payloads were deployed by the rocket, each with sensors to measure the magnetic field and the electric field so that the way they change over time and in different positions could be observed. The measurements require accurate knowledge of the spacecraft orientation, and to that end this …

Computational Fluid Dynamics Simulations Of Oscillating Wings And Comparison To Lifting-Line Theory, Megan Keddington

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Computational fluid dynamics (CFD) analysis was performed in order to compare the solutions of oscillating wings with Prandtl’s lifting-line theory. Quasi-steady and steady-periodic simulations were completed using the CFD software Star-CCM+. Quasi-steady simulations were completed for both twodimensional and three-dimensional setups. The steady-periodic simulations were only performed using a three-dimensional setup. The simulations were performed for nine separate frequencies in a pure plunging setup. An additional four simulations were then completed using a setup of combined pitching and plunging at four separate frequencies. Results from the CFD simulations were compared to the quasi-steady lifting-line solution in the form of the …

Direct Electrical Arc Ignition Of Hybrid Rocket Motors, Michael I. Judson Jr.

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Hybrid rockets motors provide distinct safety advantages when compared to traditional liquid or solid propellant systems, due to the inherent stability and relative inertness of the propellants prior to established combustion. As a result of this inherent propellant stability, hybrid motors have historically proven difficult to ignite. State of the art hybrid igniter designs continue to require solid or liquid reactants distinct from the main propellants. These ignition methods however, reintroduce to the hybrid propulsion system the safety and complexity disadvantages associated with traditional liquid or solid propellants. The results of this study demonstrate the feasibility of a novel direct …