Aerospace Engineering Commons^™

Assessing The Potential For Improved Scramjet Performance Through Application Of Electromagnetic Flow Control, Martin F. Lindsey

Theses and Dissertations

Hypersonic flight using scramjet propulsion bridges the gap between turbojets and rockets. Recent efforts focus on magnetogasdynamic (MGD) flow control to mitigate the problems of high thermomechanical loads and low efficiencies associated with scramjets. This research is the first flight-scale, three-dimensional computational analysis of a realistic scramjet to assess how MGD flow control improves scramjet performance. Developing a quasi-one dimensional design tool culminated in the first open source scramjet geometry. This geometry was tested with the Air Force Research Laboratory's electromagnetic computational code. To increase fidelity, an algorithm was developed to incorporate thermochemistry, resulting in the only open-source model of …

Spatially-Resolved Temperature Diagnostic For Supersonic Flow Using Cross-Beam Doppler-Limited Laser Saturation Spectroscopy, Grady T. Phillips

Theses and Dissertations

Optical techniques for measuring the temperature in three-dimensional supersonic reactive flows have typically depended on lineshape measurements using single-beam laser absorption spectroscopy. However, absorption over extended path lengths in flows with symmetric, turbulent eddies can lead to systematically high extracted temperatures due to Doppler shifts resulting from flow along the absorption path. To eliminate these problems, Cross-Beam Saturation Absorption Spectroscopy (CBSAS) and Cross-Beam Inter-Modulated Fluorescence (CBIMF) have been developed which utilize two crossed and nearly copropogating laser beams.to record the spectral signal of an I₂ ro-vibrational line in a small three-dimensional volume using a tunable CW dye laser. Temperature …

Control Demonstration Of A Thin Deformable In-Plane Actuated Mirror, Gina A. Peterson

Theses and Dissertations

Current imaging satellites are limited in resolution and coverage area by the aperture size of their primary optical mirror. To get a large optical mirror into space, current launch weight and size restrictions must be overcome. Membrane-like optical mirrors can overcome these restrictions with their very lightweight and flexible properties. However, thin, deformable membrane mirrors are very susceptible to the space environment and require active control for surface stabilization and shaping. The primary goal of this research is to demonstrate that an in-plane actuated membrane-like deformable optical mirror can be controlled to optical wavelength tolerances in a closed-loop system. Fabrication …

Macroscopic Computational Model Of Dielectric Barrier Discharge Plasma Actuators, Timothy R. Klein

Theses and Dissertations

Recent progress in the generation and sustainment of gas discharges at atmospheric pressure has energized research in the field of plasma-aerodynamics. Plasma actuators are promising devices that achieve flow control with no moving parts, do not alter the airfoil shape and place no parts in the flow. The operation of a plasma actuator is examined using a macroscopic (force and power addition) computational fluid dynamic model of a dielectric barrier discharge, DBD, in Fluent. A parametric approach is adopted to survey the range of requisite magnitudes of momentum and energy delivered to the flow field and to identify the effects …

Response To "Comment On Variational Approach To The Volume Viscosity Of Fluids" [Phys. Fluids 18, 109101 (2006)], Allen J. Zuckerwar, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

We respond to the Comment of Markus Scholle and therewith revise our material entropy constraint to account for the production of entropy. (c) 2006 American Institute of Physics.

Variational Approach To The Volume Viscosity Of Fluids, Allan J. Zuckerwar, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

The variational principle of Hamilton is applied to develop an analytical formulation to describe the volume viscosity in fluids. The procedure described here differs from those used in the past in that a dissipative process is represented by the chemical affinity and progress variable (sometimes called "order parameter") of a reacting species. These state variables appear in the variational integral in two places: first, in the expression for the internal energy, and second, in a subsidiary condition accounting for the conservation of the reacting species. As a result of the variational procedure, two dissipative terms appear in the Navier-Stokes equation. …

Adaptive Harmonic Balance Method For Unsteady, Nonlinear, One-Dimensional Periodic Flows, Raymond C. Maple

Theses and Dissertations

A new adaptive split-domain harmonic balance computational fluid dynamics (CFD) method is developed to solve highly nonlinear time-periodic flows such as those found in turbomachinery. The basic harmonic balance CFD method transforms an unsteady time-periodic problem into a steady-state problem by assuming a solution in the form of a Fourier series in time. The new method employs a unique multi-domain split-operator solution technique to remove a large-series stability restriction present in previous harmonic balance CFD approaches. In addition, the new method adapts the frequency content to the flow, starting with a small number of Fourier frequencies and augmenting the frequency …

Computational Aerodynamic Analysis Of The Flow Field About A Hypervelocity Test Sled, Andrew J. Lofthouse

Theses and Dissertations

The flow field about the nose section of a hypervelocity test sled is computed using computational fluid dynamics. The numerical model of the test sled corresponds to the Nike O/U narrow gage sled used in the upgrade program at the High Speed Test Track facility, Holloman Air Force Base, New Mexico. The high temperatures and pressures resulting from the aerodynamic heating and loading affect the sled structure and the performance of the vehicle. The sled transitions from an air environment to a helium environment at a speed of approximately 3,300 feet per second (Mach 3 in air, Mach 1.02 in …

Atmospheric Turbulence Conditions Leading To Focused And Folded Sonic Boom Wave Fronts, Andrew A. Piacsek

All Faculty Scholarship for the College of the Sciences

The propagation and subsequent distortion of sonic booms with rippled wave fronts are investigated theoretically using a nonlinear time-domain finite-difference scheme. This work seeks to validate the rippled wave front approach as a method for explaining the significant effects of turbulence on sonic booms [A. S. Pierce and D. J. Maglieri, J. Acoust. Soc. Am. 51, 702–721 (1971)]. A very simple description of turbulence is employed in which velocity perturbations within a shallow layer of the atmosphere form strings of vortices characterized by their size and speed. Passage of a steady-state plane shock front through such a vortex layer …

Advances In Space Radiation Shielding Codes, John W. Wilson, Ram K. Tripathi, Garry D. Qualls, Francis A. Cucinotta, Richard E. Prael, John W. Norbury, John H. Heinbockel, John Tweed, Giovanni De Angelis

Mathematics & Statistics Faculty Publications

Early space radiation shield code development relied on Monte Carlo methods and made important contributions to the space program. Monte Carlo methods have resorted to restricted one-dimensional problems leading to imperfect representation of appropriate boundary conditions. Even so, intensive computational requirements resulted and shield evaluation was made near the end of the design process. Resolving shielding issues usually had a negative impact on the design. Improved spacecraft shield design requires early entry of radiation constraints into the design process to maximize performance and minimize costs. As a result, we have been investigating high-speed computational procedures to allow shield analysis from …

Reduced Order Modeling For High Speed Flows With Moving Shocks, David J. Lucia

Theses and Dissertations

The use of Proper Orthogonal Decomposition (POD) for reduced order modeling (ROM) of fluid problems is extended to high-speed compressible fluid flows. The challenge in using POD for high-speed flows is presented by the presence of moving discontinuities in the flow field. To overcome these difficulties, a domain decomposition approach is developed that isolates the region containing the moving shock wave for special treatment. The domain decomposition implementation produces internal boundaries between the various domain sections. The domains are linked using optimization-based solvers which employ constraints to ensure smoothness in overlapping portions of the internal boundary. This approach is applied …

Modeling Axisymmetric Optical Precision Piezoelectric Membranes, James W. Rogers Jr.

Theses and Dissertations

The US Department of Defense (DOD), as well as the National Aeronautics and Astronautics Administration (NASA) and the Jet Propulsion Laboratory (JPL) are interested in developing and deploying precise, compliant, light-weight, space-based structures. More specifically, the Air Force’s core competencies ‘Aerospace Superiority’ and ‘Information Superiority’ demand ever-increasing depth and breadth of capability. Whether used for energy transmission or optical reconnaissance, current launch restraints limit rigid space-based optical reflector size. To support this requirement, the Air Force Research Laboratory (AFRL) is developing a large space-based optical membrane telescope. Inflatable reflectors can conceptually break this barrier, but controlling such a compliant structure …

Computational Fluid Dynamic Study Of A Nascar Winston Cup Series Race Car, Terry L. Meek Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

Since the goal of NASCAR racing is to win and since drag is a force the vehicle must overcome, a thorough understanding of the drag generating airflow around and through the automobile is greatly desired. The external airflow contributes to most of the drag that a car experiences and most of the downforce the vehicle produces. Therefore, an estimate of the vehicle's performance may be evaluated using a computational aerodynamics model. This thesis presents a computational fluid dynamic (CFD) analysis of a NASCAR Winston Cup series race car to investigate the salient flow characteristics.

Before a computational analysis could be …

Optical Metrology Of Adaptive Membrane Mirrors, John W. Wagner

Theses and Dissertations

Current space-based imaging platforms are significantly constrained in both size and weight by the launch vehicle. Increased payload size and weight results in increased cost and a decrease in launch responsiveness. The USAF Scientific Advisory Board (SAB) identified "Large lightweight structures for optics and antennas" as a revolutionary primary technology to be developed for the Air Force of the 21st Century. A membrane primary mirror in a space-based imaging system has the ability to overcome current payload constraints and meet evolutionary needs of the future. The challenge of membrane optics in space is the process of implementing adaptive optics technology …

Efficient Dynamic Unstructured Methods And Applications For Transonic Flows And Hypersonic Stage Separation, Xiaobing Luo

Mechanical & Aerospace Engineering Theses & Dissertations

Relative-moving boundary problems have a wide variety of applications. They appear in staging during a launch process, store separation from a military aircraft, rotor-stator interaction in turbomachinery, and dynamic aeroelasticity.

The dynamic unstructured technology (DUT) is potentially a strong approach to simulate unsteady flows around relative-moving bodies, by solving time-dependent governing equations. The dual-time stepping scheme is implemented to improve its efficiency while not compromising the accuracy of solutions. The validation of the implicit scheme is performed on a pitching NACA0012 airfoil and a rectangular wing with low reduced frequencies in transonic flows. All the matured accelerating techniques, including the …

Vortex Wake And Exhaust Plume Interaction, Including Ground Effect, Ihab Gaber Adam

Mechanical & Aerospace Engineering Theses & Dissertations

Computational modeling and studies of the near-field wake-vortex turbulent flows, far-field turbulent wake-vortex/exhaust-plume interaction for subsonic and High Speed Civil Transport (HSCT) airplane, and wake-vortex/exhaust-plume interaction with the ground are carried out. The three-dimensional, compressible Reynolds-Averaged Navier-Stokes (RANS) equations are solved using the implicit, upwind, Roe-flux-differencing, finite-volume scheme. The turbulence models of Baldwin and Lomax, one-equation model of Spalart and Allmaras and two-equation shear stress transport model of Menter are implemented with the RANS solver for turbulent-flow modeling.

For the near-field study, computations are carried out on a fine grid for a rectangular wing with a NACA-0012 airfoil section and …

Shock Waves In Nonequilibrium Gases And Plasmas, William M. Hilbun

Theses and Dissertations

An analysis and assessment of three mechanisms describing plasma/shock wave interactions was conducted under conditions typically encountered in a weakly ionized glow discharge. The mechanisms of ion-acoustic wave damping, post-shock energy addition and thermal inhomogeneities were examined by numerically solving the Euler equations with appropriate source terms adapted for each mechanism. Ion-acoustic wave damping was examined by modeling the partially ionized plasma as two fluids in one spatial dimension using the Riemann problem as a basis. Post-shock energy addition in the form of nonequilibrium vibrational energy relaxation was also examined in one spatial dimension using the Riemann problem as a …

A System For Collecting Milligram Quantities Of Cloud Condensation Nuclei, Darryl J. Alofs, Donald E. Hagen, Steven D. Medley, Daniel R. White, John L. Schmitt, Allen L. Williams

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An Experimental System to Collect Cloud Condensation Nuclei (CCN) Onto Filters in Amounts Sufficient for Chemical Analysis is Described. This Experimental Apparatus is Designed to Process Ambient Air at a Rate of More Than 1 M3/min. Two Identical Systems Have Been Built. One is Installed in a Laboratory at Rolla, MO. the Other is Installed on an 11 M Long Trailer. the System Isolates Three Size Classes of CCN, Having Mass Median Diameters of 0.27, 0.12, and 0.075 Μm, Respectively, and Mass Collection Rates of 11.5, 1.28, and 0.13 Mg/day, Respectively. the above Sizes and Collection Rates Are Obtained from …

A Study Of The Numerical Implementation Of Multidisciplinary Design Optimization Strategies, Rodney A. Taylor

Mechanical & Aerospace Engineering Theses & Dissertations

Design optimization provides an organized, systematic, and efficient method for obtaining design improvements based upon a specified measure of design performance. In the multidisciplinary design optimization (MDO) environment efficient optimization techniques allow complex designs to be improved by managing conflicting disciplinary design goals so as to improve the global design. This thesis studies the implementation issues surrounding MDO techniques and strategies. To facilitate this investigation two testbed problems have been selected for study. These problems consider two approaches to the conceptual design of an aeroelastic wing. The first approach is based on an idealized, two-dimensional representation of an airfoil under …

Wing-Section Optimization For Supersonic Viscous Flow, Cem Cihan Item

Mechanical & Aerospace Engineering Theses & Dissertations

The recent interest in the High Speed Civil Transport (HSCT) has resulted in renewed research studies of optimized supersonic cruise transport configurations. Incorporation of flow viscosity effects in the design process of such a supersonic wing is currently under investigation. This may lead to more accurate problem formulations and, in tum, greater aerodynamic efficiency than can be obtained by the traditional, inviscid, linear theories. In this context, for a design code to be a candidate for a complex optimization problem, such as three-dimensional viscous supersonic wing design, it should be validated using simpler building-block shapes.

To optimize the shape of …

Intercomparison Between Commercial Condensation Nucleus Counters And An Alternating Temperature Gradient Cloud Chamber, Darryl J. Alofs, C. K. Lutrus, Donald E. Hagen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Three Commercial CNC Counters (TSI Models 3010, 3022A, and 3025A) Are Compared with an Alternating Temperature Gradient Cloud Chamber (ALGR). Electrically Size Classified Aerosols of Sodium Chloride and Silver Are Used. Diffusional Losses within the ALGR Are Much Larger Than for the TSI Instruments: Therefore the ALGR Concentrations Are Corrected for Internal Diffusional Losses, But the TSI Instruments Are Not. the Particle Size Range Tested is 4–90 Nm. for Sodium Chloride, the TSI Concentrations Agreed Fairly Well with the Corrected ALGR at Larger Sizes, and Were Below the Corrected ALGR at Smaller Sizes. the Electrical Aerosol Classifier (EAC) Setting at …

Flow Visualization Of A Turbulent Shear Flow Using An Optical Wavefront Sensor, Daniel W. Jewell

Theses and Dissertations

The research reported here investigated the use of a shearing interferometer (SI) wavefront sensor to determine the effects of shear-layer turbulence on an optical wavefront. A collimated helium-neon laser beam was propagated through a plane shear-layer produced by mixing helium and nitrogen at different velocities. Since the gases have different indices of refraction, the optical wavefront was distorted by different amounts by each gas. The SI measured the wavefront slope across the sampled area of the wavefront. The shear-layer was viewed from two orthogonal directions. This document contains shadow graphs, interference patterns imaged by each of the SI's six cameras, …

Simulation Of Active Control Of Asymmetric Flows Around Slender Pointed Forebodies, Hazem Sharaf El-Din

Mechanical & Aerospace Engineering Theses & Dissertations

At high angles of attack, the flowfield over slender forebodies becomes asymmetric with substantial side force, which may exceed the available control capability. The unsteady compressible Navier-Stokes equations are used to investigate the effectiveness of different active control methods to alleviate and possibly eliminate the flow asymmetry and the subsequent side force. Although the research work focuses on active control methods, a passive control method has been investigated. The implicit, Roe flux-difference splitting, finite volume scheme is used for the numerical computations. Both locally-conical and three-dimensional solutions of the Navier-Stokes equations are obtained.

The asymmetric flow over five-degree semi-apex angle …

Investigation Of Computational And Spectral Analysis Methods For Aeroacoustic Wave Propagation, Florence Odile Vanel

Mechanical & Aerospace Engineering Theses & Dissertations

Most computational fluid dynamics (CFD) schemes are not adequately accurate for solving aeroacoustics problems, which have wave amplitudes several orders of magnitude smaller yet with frequencies larger than the flow field variations generating the sound. Hence, a computational aeroacoustics (CAA) algorithm should have minimal dispersion and dissipation features. A dispersion relation preserving (DRP) scheme is, therefore, applied to solve the linearized Euler equations in order to simulate the propagation of three types of waves, namely: acoustic, vorticity, and entropy waves. The scheme is derived using an optimization procedure to ensure that the numerical derivatives preserve the wave number and angular …

Unsteady Flow Simulations About Moving Boundary Configurations Using Dynamic Domain Decomposition Techniques, Guan-Wei Yen

Mechanical & Aerospace Engineering Theses & Dissertations

A computational method is developed to solve the coupled governing equations of an unsteady flowfield and those of rigid-body dynamics in six degrees-of-freedom (6-DOF). This method is capable of simulating the unsteady flowfields around multiple component configurations with at least one of the components in relative motion with respect to the others. Two of the important phenomena that such analyses can help us to understand are the unsteady aerodynamic interference and the boundary-induced component of such a flowfield. By hybridizing two dynamic domain decomposition techniques, the grid generation task is simplified, the computer memory requirement is reduced, and the governing …

Flow Simulations About Steady-Complex And Unsteady Moving Configurations Using Structured-Overlapped And Unstructured Grids, James Charles Newman Iii

Mechanical & Aerospace Engineering Theses & Dissertations

The limiting factor in simulating flows past realistic configurations of interest has been the discretization of the physical domain on which the governing equations of fluid flow may be solved. In an attempt to circumvent this problem, many Computational Fluid Dynamic (CFD) methodologies that are based on different grid generation and domain decomposition techniques have been developed. However, due to the costs involved and expertise required, very few comparative studies between these methods have been performed. In the present work, the two CFD methodologies which show the most promise for treating complex three-dimensional configurations as well as unsteady moving boundary …

Multigrid Acceleration Of Time-Dependent Solutions Of Navier-Stokes Equations, Sarafa Oladele Ibraheem

Mechanical & Aerospace Engineering Theses & Dissertations

Recent progress in Computational Fluid Dynamics is encouraging scientists to look at fine details of flow physics of problems in which natural unsteady phenomena have hitherto been neglected. The acceleration methods that have proven very successful in steady state computations can be explored for time dependent computations. In this work, an efficient multigrid methods is developed to solve the time-dependent Euler and Navier-Stokes equations. The Beam-Warming ADI method is used as the base algorithm for time stepping calculations. Application of the developed algorithm proved very efficient in selected steady and unsteady test problems. For instance, the inherent unsteadiness present in …

Simulation Of Vertical Tail Buffet In Internal Vortex Breakdown Flows, Mark William Flanagan

Mechanical & Aerospace Engineering Theses & Dissertations

Computational simulation of vertical tail buffet in an internal vortex breakdown flow is considered. The fiuid-flow problem is formulated using the full, compressible, unsteady Navier-Stokes equations which are solved using an implicit, flux-difference splitting, finite volume scheme. The fluid-flow problem is solved in a configured circular duct using quasi-axisymmetric assumptions to simplify the flow equations. A plate is placed transverse to the incoming flow. Solution of the flow in the duct is performed with and without a rigid plate, and with and without an elastic plate. The elastic response of the plate is calculated assuming that it is a cantilever …

Determining The Chemical Composition Of Cloud Condensation Nuclei, Allen L. Williams, Jane E. Rothert, Kent E. Mcclure, Darryl J. Alofs, Donald E. Hagen, Daniel R. White, A. R. Hopkins, Max B. Trueblood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This second progress report describes the status of the project one and one-half years after the start. The goal of the project is to develop the instrumentation to collect cloud condensation nuclei (CCN) in sufficient amounts to determine their chemical composition, and to survey the CCN composition in different climates through a series of field measurements. Our approach to CCN collection is to first form droplets on the nuclei under simulated cloud humidity conditions, which is the only known method of identifying CCN from the background aerosol. Under cloud chamber conditions, the droplets formed become larger than the surrounding aerosol, …

Hydration Behavior Of Laser Dye Aerosols Of Mixed Composition Having High Critical Supersaturations, Max B. Trueblood, Donald E. Hagen, Darryl J. Alofs

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This Study Concerns Aerosol Particles of Mixed Composition. the Particles Contain a Water Insoluble Core (Polystyrene Latex), Surrounded by a Water Soluble Shell (Various Fluorescent Dyes). a Collison Nebulizer and an Electrostatic Aerosol Classifier Are Used to Prepare the Aerosol; its Critical Supersaturation Spectrum is Measured with a Diffusion Cloud Chamber. Experiments Were Done using Four Different Dyes (Disodium Fluorescein, Sulforhodamine 640, Sulforhodamine B and Rhodamine 560 Chloride) with Five Different Polystyrene Latex Sphere Sizes. the Results Indicate that a Kohler-Type Behavior is Obeyed. This Technique of Putting a Soluble Coating Onto an Insoluble Core is Found to Be a …