Engineering Commons^™

Numerical Study Of A Transpiration Cooled Rocket Nozzle, Jay A. Landis

Theses and Dissertations

This study proved that transpiration cooling provides a better cooling scheme than regenerative cooling for long operating duration, liquid-fueled rocket engine nozzles. This proof was made on the basis of maximum wall temperature. This study compared transpiration cooling to regenerative cooling in the throat region of the Space Shuttle Main Engine Main Combustion Chamber. The study also analyzed the effects of porosity, solid thermal conductivity, and porous sphere size on a porous wall made of packed spheres. The transpiration cooled nozzle operated 35% cooler than a regeneratively cooled nozzle, but the temperature gradient at the hot gas surface was 72 …

Full Lyapunov Exponent Placement In Reentry Trajectories, Michael H. Platt

Theses and Dissertations

This study investigated the ability to control the chaotic reentry of a Delta-Clipper like vehicle by setting the values of initial arid final principal dynamical directions as well as the Lyapunov exponents. A model of the original controlled reentry vehicle was created through the use of the equations of motion in conjunction with an atmospheric model. A modified linear quadratic regulator allowed the set up of a boundary value problem which specified the Lyapunov exponents and determined the gain matrix as a function of time. The gain matrix can eventually be used in the control system of the vehicle.

Sub-Optimal Control Of Rigid Spacecraft Reorientation Using Three Momentum Wheels, Gregory W. Schultz

Theses and Dissertations

This thesis addresses sub-optimal employment of 3 momentum wheels for large angle reorientation of rigid spacecraft with minimal induced spacecraft motion during maneuvers. In addition to development of general theory for 3 wheel vehicles, simulation results for a vehicle using momentum wheels for secondary attitude control (GPS Block IIR) are compared to results for a vehicle using them for primary attitude control (the Hubble Space Telescope), to demonstrate practical applications and limitations. While the control laws were developed assuming no external perturbing torques on the vehicle, reorientation scenarios were run both in a torque free environment as well as an …

A Quantitative Feedback Theory Fcs Design For The Subsonic Envelope Of The Vista F-16 Including Configuration Variation And Aerodynamic Control Effector Failures, Vicent J. Cacciatore

Theses and Dissertations

Fault tolerant flight control systems for combat aircraft are an alternative to excessively redundant aircraft designs or reconfigurable control laws. However, due to the range of flight conditions within a combat aircraft's operational flight envelope, the variety of its configurations, and the unavailability of an aerodynamic data base for damaged aircraft, designing fault tolerant systems is a complicated endeavor. Quantitative Feedback Theory is a robust control design technique especially well-suited to manage the structured parametric uncertainty inherent in this problem, and consequently is applied as the primary design tool for this research. Furthermore, realistic failure models are developed for the …

Design And Analysis Of A Navigation System Using The Federated Filter, Stephen J. Delory

Theses and Dissertations

The purpose of this paper was to design and analyse a federated filter design, to be used for retrofit of an Embedded GPS/INS (EGI) navigation unit into an existing Kalman filter-based air navigation system. A design was selected and simulations were conducted in the Distributed Kalman Filter Simulation software (DKFSIM). As well, a centralized Kalman filter design was simulated under identical conditions for comparison purposes. The federated filter was shown to be a feasible design, with accuracy in position and velocity very close to centralized Kalman filter values. The federated filter design also showed some attractive fault detection and isolation …

Analysis Of Gravity-Gradient Satellite Attitude Inversion, Jules-Francois D. Desamours

Theses and Dissertations

The purpose of this research is to understand and describe the process by which the 1986 Polar BEAR gravity- gradient research satellite of John Hopkins University/Applied Physics Laboratory achieved an orbital attitude correction (re-inversion) from an inverted orientation through the utilization of its momentum wheel. Understanding this process provides an analytical foundation from which a universal attitude inversion process for other gravity-gradient satellites with similar anomalous motions may be sought and developed. The equations of motion for a gravity-gradient satellite with a momentum wheel are derived and implemented in FORTRAN for simulation of the dynamics of the spacecraft. Several re-inversion …

Systems Analysis Of Gps Electrical Power System Redesign, Kevin J. Walker

Theses and Dissertations

A systematic analysis is applied to the electrical power subsystem of the Global Positioning Satellite (GPS) system. Results determined the most appropriate power source and conversion system Options. Photovoltaic solar arrays, the current power system, were not included in the analysis. The best electrical power subsystem options found in the analysis include a solar power source with either a dynamic or direct conversion technique, and a direct conversion nuclear source. The two solar options are designed, at a low level of detail, to provide the same level of power the current GPS photovoltaic solar array system provides. These two designs …

Development And Testing Of A New Optimum Design Code For Hypersonic Wind Tunnel Nozzles, Including Boundary Layer, Turbulence, And Real Gas Effects, Ralph C. Tolle

Theses and Dissertations

A robust and efficient optimization code is developed and validated. The code is used to redesign an existing Mach 12 wind tunnel nozzle and utilizes response surface methodology (RSM) techniques. Explicit, globally second-order, flux-difference-splitting algorithms are used to solve the Navier-Stokes (NS) and Parabolized Navier-Stokes (PNS) flow solvers incorporated into the optimizer code. Either the Baldwin-Lomax or the Yang-Shih k-s turbulence model may be employed in the optimization code. First, 2-D/axisymmetric NS and PNS flow solvers are developed/modified and account for perfect gas/nonequilibrium chemically reacting flows. All solvers are validated against Computational Fluid Dynamics (CFD) and experimental data. The optimization …

The Evolution And Testing Of An Aerovalve Pulsejet Engine, Gregory V. Meholic

Master's Theses - Daytona Beach

The goal of this project was to develop and test a self-aspirating aerovalve pulsejet and measure its operating characteristics. An investigation of pulsejets developed by previous experimenters revealed design trends associated with the engine geometry. These trends were followed in the development of an aerovalve pulsejet engine entitled the Astra. The engine employed variable fuel injection methods, ignition location and exhaust pipe length to show that certain combinations of geometry relations and fuel injection methods were more conducive to pulse combustion. Even though the engine pulsed with forced inlet air, the Astra did not self-aspirate as did the engines …

An Experimental Investigation Of Wall Cooling Effects On Hypersonic Boundary Layer Stability In A Quiet Wind Tunnel, Alan E. Blanchard

Mechanical & Aerospace Engineering Theses & Dissertations

One of the primary reasons for developing quiet tunnels is for the investigation of high-speed boundary-layer stability and transition phenomena without the transition-promoting effects of acoustic radiation from tunnel walls. In this experiment, a flared-cone model under adiabatic- and cooled-wall conditions was placed in a calibrated, 'quiet' Mach 6 flow and the stability of the boundary layer was investigated using a prototype constant-voltage anemometer. The results were compared with linear-stability theory predictions and good agreement was found in the prediction of second-mode frequencies and growth. In addition, the same 'N=10' criterion used to predict boundary-layer transition in subsonic, transonic, and …

Buckling Analysis And Optimum Design Of Multidirectionally Stiffened Composite Curved Panel, Navin R. R. Jaunky

Mechanical & Aerospace Engineering Theses & Dissertations

Continuous filament grid-stiffened structure is a stiffening concept that combines structural efficiency and damage tolerance. However, buckle resistant design optimization of such structures using a finite element method is expensive and time consuming due to the number of design parameters that can be varied. An analytical optimization procedure which is simple, efficient and supports the preliminary design of grid-stiffened structures for application to combined loading cases is needed.

An analytical model for a general grid-stiffened curved panel is developed using an improved smeared theory with a first-order, shear-deformation theory to account for transverse shear flexibilities and local skin-stiffener interaction effects. …

Nonlinear Geometric And Material Behavior Of Composite Shells With Large Strains, Scott A. Schimmels

Theses and Dissertations

A two-dimensional, geometrically and materially nonlinear shell theory applicable to arbitrary geometries described by orthogonal curvilinear coordinates and encompassing large displacements, moderate rotations for large strain situations has been developed. Additionally, the theory includes Jacobian transformation matrices, based upon displacement parameters, for the Cauchy - 2nd Piola-Kirchhoff stress-state and the Cauchy (Almansi) - Green strain-state transformations, and a layered material approach is included for the elastoplastic analysis to allow for variation of plasticity through-the-thickness. Doubly curved 20, 28, and 36 degree-of-freedom finite elements are defined based on specialization of the theory to spherical coordinates. The computer program includes algorithms for …

A Direct Synthesis Method For The Conceptual Design Of Transport Aircraft, Pierre Andre Fruytier

Master's Theses - Daytona Beach

The problem of synthesizing a transport aircraft at the conceptual design level is considered. A direct sizing algorithm that does not require iteration is developed. Such direct synthesis methods can be used as important building blocks in an aircraft optimization process. New statistical equations based on current aircraft are derived for approximating the widths and lengths of the cabin and fuselage. A more accurate static thrust over gross weight, which is based on the equations of motion specified by the FAR part 25 climb requirements, is presented. A cruise at constant altitude with optional step-climb is taken into account. The …

The Dependence Of The Time-Asymptotic Structure Of 3-D Vortex Breakdown On Boundary And Initial Conditions, Jeffrey C. Tromp

Theses and Dissertations

The three-dimensional, compressible Navier-Stokes equations are solved numerically to simulate vortex breakdown in tubes. Time integration is performed with an implicit Beam-Warming algorithm, which uses fourth-order compact operators to discretize spatial derivatives. Initial conditions are obtained by solving the steady, compressible, and axisymmetric form of the Navier-Stokes equations using Newton's method. Stability of the axisymmetric initial conditions is assessed through 3-D time integration. Unique axisymmetric solutions at a Reynolds number of 250 lose stability to 3-D disturbances at a critical value of vortex strength, resulting in 3-D and time-periodic flow. Axisymmetric solutions at a Reynolds number of 1000 contain regions …

Numerical Investigation Of Shock-Induced Combustion Past Blunt Projectiles, Jagjit K. Ahuja

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical study is conducted to simulate shock-induced combustion in premixed hydrogen-air mixtures at various free-stream conditions and parameters. Two-dimensional axisymmetric, reacting viscous flow over blunt projectiles is computed to study shock-induced combustion at Mach 5.11 and Mach 6.46 in hydrogen-air mixture. A seven-species, seven reactions finite rate hydrogen-air chemical reaction mechanism is used combined with a finite-difference, shock-fitting method to solve the complete set of Navier-Stokes and species conservation equations. In this approach, the bow shock represents a boundary of the computational domain and is treated as a discontinuity across which Rankine-Hugoniot conditions are applied. All interior details of …

Dynamic Unstructured Method For Prescribed And Aerodynamically Determined Relative Moving Boundary Problems, Kamakhya Prasad Singh

Mechanical & Aerospace Engineering Theses & Dissertations

A new methodology is developed to simulate unsteady flows about prescribed and aerodynamically determined moving boundary problems. The method couples the fluid dynamics and rigid-body dynamics equations to capture the time-dependent interference between stationary and moving boundaries. The unsteady, compressible, inviscid (Euler) equations are solved on dynamic, unstructured grids by an explicit, finite-volume, upwind method. For efficiency, the grid adaptation is performed within a window around the moving object. The Eulerian equations of the rigid-body dynamics are solved by a Runge-Kutta method in a non-inertial frame of reference. The two-dimensional flow solver is validated by computing the flow past a …

Effects Of Blowing Ratios On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Fu-Jung Chen

Theses and Dissertations

The effects of transpiration cooling on heat transfer in the throat region of a porous-walled nozzle were investigated. The experiments were performed in the AFIT low speed shock tube fitted with a Mach 2 nozzle. A blowing region was limited to the area from 1.3 cm prior to the throat to 1.2 cm downstream of the throat. The blowing ratios from -0.0002 (suction) to 0.0117 (blowing) of the main stream flow were studied. Heat flux data were taken from both sides of the nozzle. One side was transpiration cooled by secondary air injection through a porous wall, while the other …

Dynamic Simulation Of General Aviation Cabin Environments And Occupant Restraint Systems, Mark A. Shilladay

Master's Theses - Daytona Beach

After a five year study of General Aviation (GA) accidents, the National Transportation Safety Board (NTSB) has concluded that aircraft cabin environments place the occupant at high risk of suffering severe injuries in an emergency crash situation. Studies of Federal Aviation Administration (FAA) seat tests were used to form the basis of a computer analysis to address dynamic cabin environments. In this effort a simplified system of masses, springs, and dampers are used to simulate the more complex configuration of cabin structure, seat, pilot, and restraints on a personal computer. The primary objective of this study is to accurately simulate …

Advanced Rover Chassis, Eric Alan Poulson, Collin Lewis, Todd Graves

Undergraduate Honors Capstone Projects

Background:

The six wheeled rover vehicle detailed in this design is intended as an upgrade test bed for the sensor array and autonomous navigation algorithms in use by Utah State University's Center for Self-Organizing and Intelligent Systems (CSOIS). The CSOIS's sensor suite can successfully detect and avoid unnavigable obstacles up to five vehicle lengths in front of the vehicle. The center presently uses a modified RC type chassis and only supports two wheel drive. This chassis was adequate to bring the CSOIS's algorithms to a proof-of-principles state, but in order to place the system in any practical application, a full …

Standardized Checklists Versus Variable Checklist: An Evaluation In A Light Twin Simulator, Veronica Terese Cote

Master's Theses - Daytona Beach

The purpose of this study was to determine if a checklist that varied by sequence would enable the pilot to detect potential errors more easily than those who used an unchanging checklist. A flight hour based stratified sample of pilots were randomly divided into two groups and flew a series of eight flights in a light twin aircraft simulator. The control group used the same checklist for each trial; the experimental group used a checklist that covered the same items but varied in sequence for each trial. Faults were introduced in the last two trials. The number of faults discovered …

An Experimental Study Of Transient Flows In Pulse Combustors, Michael P. Femandes

Master's Theses - Daytona Beach

The purpose of this investigation was to experimentally characterize a pulse combustor with respect to ambient conditions, pressure amplitudes, wall temperature, combustor geometry and type of centerbody used. The wall temperatures were recorded and the pressure variation was obtained using a sampling rate of 10,000 readings per second. These parameters were recorded for two different tailpipe lengths and centerbodies, and for different ambient conditions. Power spectrums were then obtained from the pressure variations. These spectrums displayed the peak amplitudes and the frequencies at which they occurred. The experiment showed distinct repeatability. It was concluded that combustor displayed the steady, pulsing …

Numerical Investigation Of Second-Order Effects In A Supersonic Boundary-Layer, Timothy R. Membrino

Master's Theses - Daytona Beach

Historically, the study of boundary-layer flows has centered on the analysis of the first-order boundary-layer equations and their application to physical flow problems. However, selected “real-world” boundary-layer flows exhibit significant second-order effects which are neglected by the first-order equations. Full Navier-Stokes solutions are often not merited or desired for these flows. Therefore, the second-order boundary-layer equations provide a compromise.

Few validating comparisons have been attempted between second-order boundary-layer theory and experimental or numerical solutions of compressible viscous flows. Experimental simulations to capture second-order effects are difficult since the desired effects are small and can exist simultaneously, resulting in a neutralizing …

Classification Of Acoustic Emission Signals From An Aluminum Pressure Vessel Using A Self-Organizing Map, Weldon Paul Thornton

Master's Theses - Daytona Beach

Acoustic emission nondestructive testing has been used for real-time monitoring of complex structures. All of the structures were made of materials at least 0.070 inch thick. The purpose of this research was to demonstrate the feasibility of using neural networks to classify acoustic emission signals gathered from a pressure vessel made of 2024-T3 aluminum 0.040 inches thick, i.e. thin aluminum sheet. AE waveforms were recorded during fatigue cycling of one pressure vessel using a wide band transducer and a digital oscilloscope connected to a computer. The source for each signal was determined using two narrow band transducers and a LOCAN-AT …

An Experimental Study Of Transient Flows In Pulse Combustors, Michael P. Fernandes

Doctoral Dissertations and Master's Theses

The purpose of this investigation was to experimentally characterize a pulse combustor with respect to ambient conditions, pressure amplitudes, wall temperature, combustor geometry and type of centerbody used. The wall temperatures were recorded and the pressure variation was obtained using a sampling rate of 10,000 readings per second. These parameters were recorded for two different tailpipe lengths and centerbodies, and for different ambient conditions. Power spectrums were then obtained from the pressure variations. These spectrums displayed the peak amplitudes and the frequencies at which they occurred. The experiment showed distinct repeatability. It was concluded that combustor displayed the steady, pulsing …

Aerodynamic Design Optimization With Consistently Discrete Sensitivity Derivatives Via The Incremental Iterative Method, Vamshi M. Korivi

Mechanical & Aerospace Engineering Theses & Dissertations

In this study which involves advanced fluid-flow codes, an incremental iterative formulation (also known as the "delta" or "correction" form), together with the well-known spatially split approximate-factorization algorithm, is presented for solving the large, sparse systems of linear equations that are associated with aerodynamic sensitivity analysis. For the smaller two dimensional problems, a direct method can be applied to solve these linear equations in either the standard or the incremental form, in which case the two are equivalent. However, iterative methods are needed for larger two-dimensional and three dimensional applications because direct methods require more computer memory than is currently …

Finite Element Nonlinear Random Response Of Composite Panels Of Arbitrary Shape To Acoustic And Thermal Loads Applied Simultaneously, Roger R. Chen

Mechanical & Aerospace Engineering Theses & Dissertations

The nonlinear random response of composite plates to the simultaneously applied, combined acoustic/thermal loads are investigated in this dissertation. A finite element formulation for the nonlinear random response is developed. The three-node Mindlin plate element with improved transverse shear is extended and employed. The extension includes the development of the thermal geometric matrix, the mass matrix, the first- order and second-order nonlinear stiffness matrices, and the thermal and mechanical load vectors. An innovative solution procedure has been created which is believed to be the first attempt to analyze nonlinear random response of complex composite panels subjected to simultaneous acoustic and …

Nonlinear Analysis Of Composite Beams Under Random Excitations, Snorri Gudmundsson

Master's Theses - Daytona Beach

The vibration responses of three unsymmetrically laminated beams, that are excited with a Gaussian random forcing function, are studied in this thesis. The beams are analyzed nonlinearly and compared to linear results, indicating some important corrections. The solution procedure begins with the derivation of the general equation of motion using Galerkin's method. Then, two approaches are taken in the solution. First, the equation of motion is attacked directly employing a real time Runge-Kutta numerical analysis. Second, the method of equivalent linearization is used. The thesis finds the results from the two approaches to be in a close agreement, although some …

Multipoint Quadratic Approximation For Numerical Optimization, Michael A. Blaylock

Theses and Dissertations

A quadratic approximation for nonlinear functions is developed in order to realize computational savings in solving numerical optimization problems. Function and gradient information accumulated from multiple design points during the iteration history is used in estimating the Hessian matrix. The approximate Hessian matrix is the available for a second order Taylor series approximation to the functions of interest. Several truss and frame models will be used to demonstrate the effectiveness of the new Multipoint Quadratic Approximation (MQA) in solving structural optimization problems.

A Decision Model For Environmental Assessment Of Process Waste Products, Kyle F. Byard

Theses and Dissertations

Environmental managers must compare the potential impacts of waste products when deciding upon courses of action. The estimation and comparison of these impacts is a subjective process, and few methods of comprehensive, quantitative comparison of waste products currently exist. The intent of this study is to develop a decision methodology to evaluate the environmental impacts of waste products and to score them for comparison. The method will follow established system design principles and incorporate significant characteristics of the waste material. Scores derived to represent the environmental impacts of materials will then he analyzed employing statistical and probabilistic methods to assess …

Analysis And Modeling Of An Airport Departure Process, Joseph E. Hebert

Theses and Dissertations

This study analyzes departure delays at a major airport using probability models to represent this non-homogeneous process. The models developed in this study expand on the Markovian models presently used by employing the method of stages to represent some of the model processes. This technique improves the user's ability to achieve a close fit for the service time probability distribution while maintaining the advantages of the Markovian model. The three types of models developed and compared all assume a Markovian system entry process. The first model uses an exponential distribution to model the service process. The second uses an Erlang …