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 Aerospace engineering and engineering mechanics (6)
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Articles 1  30 of 31
FullText Articles in Engineering
Compressible Flow Analysis Of Thrust Augmenting Ejectors, Mohamed Moujahid
Compressible Flow Analysis Of Thrust Augmenting Ejectors, Mohamed Moujahid
Theses  Daytona Beach
The present work was initiated due to the need for a method to understand and predict the thrust augmenting characteristics of jet ejectors. The mixing process in ejectors can be analyzed using either the control volume approach, or detailed models based on the Navier Stokes Equations and the theory of turbulent jets. The control volume approach uses integrated forms of the conservation equations of mass, momentum and energy. It is chosen in the first part of the study since it affords the best vehicle for the parametric studies required to understand the potential of ejectors for a given application. Compressibility ...
Dynamic Pulse Buckling Of Columns With Viscous Damping, Murli Kadandale
Dynamic Pulse Buckling Of Columns With Viscous Damping, Murli Kadandale
Master's Theses
This is a study of dynamic pulse buckling of columns with viscous damping. The differential equations of motion were obtained using the BemoulliNavier hypothesis. The effects of axial and rotary inertia were included in the analysis. The VoigtKelvin model for a viscoelastic material is used. The Finite Difference Method was employed to solve the differential equations of motion. First columns without geometrical imperfections were studied, and a correlation between the damping modulus and the more familiar damping ratio was obtained. Then beams with initial geometrical imperfection were studied. A suitable dynamic buckling criterion was defined. It was observed that viscous ...
The Evolution And Testing Of An Aerovalve Pulsejet Engine, Gregory V. Meholic
The Evolution And Testing Of An Aerovalve Pulsejet Engine, Gregory V. Meholic
Theses  Daytona Beach
The goal of this project was to develop and test a selfaspirating 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 selfaspirate as did the engines on ...
Buckling Analysis And Optimum Design Of Multidirectionally Stiffened Composite Curved Panel, Navin R. R. Jaunky
Buckling Analysis And Optimum Design Of Multidirectionally Stiffened Composite Curved Panel, Navin R. R. Jaunky
Mechanical & Aerospace Engineering Theses & Dissertations
Continuous filament gridstiffened 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 gridstiffened structures for application to combined loading cases is needed.
An analytical model for a general gridstiffened curved panel is developed using an improved smeared theory with a firstorder, sheardeformation theory to account for transverse shear flexibilities and local skinstiffener interaction effects ...
An Experimental Investigation Of Wall Cooling Effects On Hypersonic Boundary Layer Stability In A Quiet Wind Tunnel, Alan E. Blanchard
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 highspeed boundarylayer stability and transition phenomena without the transitionpromoting effects of acoustic radiation from tunnel walls. In this experiment, a flaredcone model under adiabatic and cooledwall conditions was placed in a calibrated, 'quiet' Mach 6 flow and the stability of the boundary layer was investigated using a prototype constantvoltage anemometer. The results were compared with linearstability theory predictions and good agreement was found in the prediction of secondmode frequencies and growth. In addition, the same 'N=10' criterion used to predict boundarylayer transition in subsonic, transonic ...
A Direct Synthesis Method For The Conceptual Design Of Transport Aircraft, Pierre Andre Fruytier
A Direct Synthesis Method For The Conceptual Design Of Transport Aircraft, Pierre Andre Fruytier
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 stepclimb is taken into account. The ...
Numerical Investigation Of ShockInduced Combustion Past Blunt Projectiles, Jagjit K. Ahuja
Numerical Investigation Of ShockInduced Combustion Past Blunt Projectiles, Jagjit K. Ahuja
Mechanical & Aerospace Engineering Theses & Dissertations
A numerical study is conducted to simulate shockinduced combustion in premixed hydrogenair mixtures at various freestream conditions and parameters. Twodimensional axisymmetric, reacting viscous flow over blunt projectiles is computed to study shockinduced combustion at Mach 5.11 and Mach 6.46 in hydrogenair mixture. A sevenspecies, seven reactions finite rate hydrogenair chemical reaction mechanism is used combined with a finitedifference, shockfitting method to solve the complete set of NavierStokes 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 RankineHugoniot conditions are applied. All interior ...
Dynamic Unstructured Method For Prescribed And Aerodynamically Determined Relative Moving Boundary Problems, Kamakhya Prasad Singh
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 rigidbody dynamics equations to capture the timedependent interference between stationary and moving boundaries. The unsteady, compressible, inviscid (Euler) equations are solved on dynamic, unstructured grids by an explicit, finitevolume, upwind method. For efficiency, the grid adaptation is performed within a window around the moving object. The Eulerian equations of the rigidbody dynamics are solved by a RungeKutta method in a noninertial frame of reference. The twodimensional flow solver is validated by computing the flow past a ...
Advanced Rover Chassis, Eric Alan Poulson, Collin Lewis, Todd Graves
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 SelfOrganizing 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 proofofprinciples state, but in order to place the system in any practical ...
Dynamic Simulation Of General Aviation Cabin Environments And Occupant Restraint Systems, Mark A. Shilladay
Dynamic Simulation Of General Aviation Cabin Environments And Occupant Restraint Systems, Mark A. Shilladay
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 ...
Standardized Checklists Versus Variable Checklist: An Evaluation In A Light Twin Simulator, Veronica Terese Cote
Standardized Checklists Versus Variable Checklist: An Evaluation In A Light Twin Simulator, Veronica Terese Cote
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 ...
Classification Of Acoustic Emission Signals From An Aluminum Pressure Vessel Using A SelfOrganizing Map, Weldon Paul Thornton
Classification Of Acoustic Emission Signals From An Aluminum Pressure Vessel Using A SelfOrganizing Map, Weldon Paul Thornton
Theses  Daytona Beach
Acoustic emission nondestructive testing has been used for realtime 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 2024T3 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 ...
Numerical Investigation Of SecondOrder Effects In A Supersonic BoundaryLayer, Timothy R. Membrino
Numerical Investigation Of SecondOrder Effects In A Supersonic BoundaryLayer, Timothy R. Membrino
Theses  Daytona Beach
Historically, the study of boundarylayer flows has centered on the analysis of the firstorder boundarylayer equations and their application to physical flow problems. However, selected “realworld” boundarylayer flows exhibit significant secondorder effects which are neglected by the firstorder equations. Full NavierStokes solutions are often not merited or desired for these flows. Therefore, the secondorder boundarylayer equations provide a compromise.
Few validating comparisons have been attempted between secondorder boundarylayer theory and experimental or numerical solutions of compressible viscous flows. Experimental simulations to capture secondorder effects are difficult since the desired effects are small and can exist simultaneously, resulting in a neutralizing ...
An Experimental Study Of Transient Flows In Pulse Combustors, Michael P. Femandes
An Experimental Study Of Transient Flows In Pulse Combustors, Michael P. Femandes
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 ...
A Computer Model For Airfoils With Moving Surface BoundaryLayer Control, Jacob Kimball
A Computer Model For Airfoils With Moving Surface BoundaryLayer Control, Jacob Kimball
Mathematics, Engineering and Computer Science Undergraduate Theses
One method that is used to enhance airplane safety and performance is to use moving surfaces on wings to increase lift. A modification of the panel method is used to model airfoils which incorporate moving surface boundarylayer control. The modification is to apply a vortex sheet of constant strength over the moving portions of the airfoil. The model is demonstrated on an airfoil that has a rotating cylinder on the leading edge. The modified panel method was programmed in Mathematica (Wolfram Research Incorporated). The results generated by the Mathematica program are displayed graphically and show an increase in lift for ...
An Experimental Study Of Transient Flows In Pulse Combustors, Michael P. Fernandes
An Experimental Study Of Transient Flows In Pulse Combustors, Michael P. Fernandes
Dissertations and 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 ...
Finite Element Nonlinear Random Response Of Composite Panels Of Arbitrary Shape To Acoustic And Thermal Loads Applied Simultaneously, Roger R. Chen
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 threenode 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 secondorder 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 ...
Aerodynamic Design Optimization With Consistently Discrete Sensitivity Derivatives Via The Incremental Iterative Method, Vamshi M. Korivi
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 fluidflow codes, an incremental iterative formulation (also known as the "delta" or "correction" form), together with the wellknown spatially split approximatefactorization 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 twodimensional and three dimensional applications because direct methods require more computer memory than is currently ...
Nonlinear Analysis Of Composite Beams Under Random Excitations, Snorri Gudmundsson
Nonlinear Analysis Of Composite Beams Under Random Excitations, Snorri Gudmundsson
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 RungeKutta 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 ...
Parallel Surface Reconstruction Through Virtual Milling , Kumaran Kalyanasundaram
Parallel Surface Reconstruction Through Virtual Milling , Kumaran Kalyanasundaram
Retrospective Theses and Dissertations
Surface definition deals with representing a surface analytically using a finite number of parameters and with acceptable levels of error. In the past few years it has become a key discipline in Computational Fluid Dynamics (CFD). Recent advances in computers and numerical algorithms have made it possible for CFD practitioners to attempt flow solutions about complex threedimensional geometries. The first step in this process is having a numerical representation of the shape. In many cases of interest such a representation already exists; i.e., aircraft designed on a computer. Such ComputerAided Design (CAD) descriptions do not exist, though, for objects ...
Numerical Investigation Of Type Ii NonNewtonian De/AntiIcing Fluid Effects On TakeOff Performance For General Aviation Aircraft , Dennis James Cronin
Numerical Investigation Of Type Ii NonNewtonian De/AntiIcing Fluid Effects On TakeOff Performance For General Aviation Aircraft , Dennis James Cronin
Retrospective Theses and Dissertations
Ground icing, while preventable with glycol based freezing point depressant fluids, accounts for nearly 4050 civil accidents a year according to one account. More viscous than Type I fluids, Type II fluids are inherently nonlinear in their shear stressrate of strain relationship having smaller relative viscosity at higher shear rates. The nonlinearity makes properly scaled windtunnel testing difficult and computational methods are employed in this study to look at the aerodynamic effects of the deicing fluid on global performance during typical takeoff maneuvers for general aviation. The method is tested on a twodimensional NACA 0012 airfoil under typical takeoff simulation ...
Adaptive Nonlinear Attitude Control Of Spacecraft , Cheng Tang
Adaptive Nonlinear Attitude Control Of Spacecraft , Cheng Tang
Retrospective Theses and Dissertations
Three adaptive nonlinear control approaches are proposed for attitude control of a Space Station. These control algorithms avoid the need for linearization, either by truncating a Taylor series or by a feedback linearization approach, which poses some difficulties in the presence of both uncertain mass properties and external disturbances. Global stability of the Space Station is guaranteed;A conventional linearquadratic regulator synthesis technique is investigated. This linear control scheme provides a natural way to select control gains for the known spacecraft system parameters. Simulation results reveal that the uncertain mass property causes the nonlinear Space Station to be uncontrollable;On ...
Optimal Turning Maneuvers For SixDegreeOfFreedom High AngleOfAttack Aircraft Models , JenNai Chou
Optimal Turning Maneuvers For SixDegreeOfFreedom High AngleOfAttack Aircraft Models , JenNai Chou
Retrospective Theses and Dissertations
Various MinimumTime Turning Maneuvers for two high angleofattack, sixdegreeoffreedom, aircraft models have been investigated. The primary aircraft model is for a nonlinear 6DOF F16 fighter aircraft with high angleofattack maneuverability. The other model is for a linearized 6DOF F18 fighter which also can be flown in the high angleofattack range. Standard 6DOF equations are employed except that the Quaternion attitude representation system is used instead of Euler Angles to avoid the pitch angle singularity of Euler Angles;These Optimal Control problems have been transformed into Nonlinear Programming problems via Parameter Optimization techniques. Different parameterization techniques were tested on the Van ...
Unstructured Grid Algorithms For Two And ThreeDimensional Flows On Parallel Computers , Thomas Hans Ramin
Unstructured Grid Algorithms For Two And ThreeDimensional Flows On Parallel Computers , Thomas Hans Ramin
Retrospective Theses and Dissertations
The NavierStokes equations are solved numerically for twoand threedimensional viscous laminar flows. The domain is discretized using triangular control volumes in two dimensions and tetrahedra in three dimensions, using existing grid generators. The flow solvers are implemented on a variety of computers, including distributed memory parallel computers;A finitevolume approach is used to discretize the governing flow equations in conservation law form using conserved variables. A cell centered approach is used where the unknowns are computed at the center of each control volume. Both explicit and implicit solution strategies are pursued. In the twodimensional version of the algorithm an explicit ...
Coupled Compressible And Incompressible Finite Volume Formulations For The Large Eddy Simulation Of Turbulent Flow With And Without Heat Transfer , WenPing Wang
Retrospective Theses and Dissertations
A coupled finite volume approach for solving the timedependent NavierStokes equations is developed for application to the large eddy simulation (LES) of turbulent flow. The preconditioning strategy of coupling the incompressible NS equations and providing acceleration of iterative convergence in both compressible and incompressible formulations is employed. Three different spatial discretization schemes along with the regular/staggered grid arrangements are evaluated on both twodimensional laminar flows and threedimensional turbulent flows;No distinctive differences are found in laminar flow cases, but the staggered grid appears to provide a better resolution of the turbulence statistics over a regular one in the simulation ...
Turbulent Scalar Transport Using TwoPoint Statistical Closure Theory , Robert Charles Sanderson
Turbulent Scalar Transport Using TwoPoint Statistical Closure Theory , Robert Charles Sanderson
Retrospective Theses and Dissertations
The turbulent transport of a passive scalar (Corrsin's problem with diffusion) and of an active scalar in stably stratified fluids is studied using linear analysis (rapid distortion theory or RDT), Kraichnan's direct interaction approximation (DIA) and direct numerical simulation (DNS). The results are compared with each other and with laboratory experiments. The numerical results compare favorably with the experiments of Sirivat and Warhaft, Budwig, Tavoularis and Corrsin and Stillinger and Itsweire of van Atta's group. The RDT study reveals that much of the qualitative behavior observed in experiments, such as the tendency for the system to evolve ...
Unstructured Surface And Volume Decimation Of Tessellated Domains , Kevin Joseph Renze
Unstructured Surface And Volume Decimation Of Tessellated Domains , Kevin Joseph Renze
Retrospective Theses and Dissertations
A general algorithm for decimating unstructured discretized data sets is presented. The discretized space may be a planar triangulation, a general 3D surface triangulation, or a 3D tetrahedrization. The decimation algorithm enforces Dirichlet boundary conditions, uses only existing vertices, and assumes manifold geometry. Local dynamic vertex removal is performed without history information while preserving the initial topology and boundary geometry. The tessellation at each step of the algorithm is preserved and, in the pathological case, every interior vertex is a candidate for removal. The research focuses on how to remove a vertex from an existing unstructured ndimensional tessellation, not on ...
A Compliant Model For Estimation And Optimization Of Damping In Vibrating Structures , Thomas Jeffrey Thompson
A Compliant Model For Estimation And Optimization Of Damping In Vibrating Structures , Thomas Jeffrey Thompson
Retrospective Theses and Dissertations
Proposed future space missions involve large structures which must maintain precise dimensional tolerances even during dynamic maneuvers. In order to attenuate disturbances in the many modes of vibration of such a structure, active and passive vibration control are proposed. The passive control is to be achieved by placing viscous or viscoelastic members or materials within a structure in order to absorb energy. Ascertaining the best combination of locations for such treatments is difficult due to the large number of cases, each of which requires computationally expensive complex eigenvalue analyses of a finite element model to compute modal damping values;In ...
Ultrasonic Nondestructive Evaluation Techniques And The Effects Of Fiber Architecture On Mechanical Performance In MultiDirectionally Reinforced Textile Composites , Richard Douglas Hale
Ultrasonic Nondestructive Evaluation Techniques And The Effects Of Fiber Architecture On Mechanical Performance In MultiDirectionally Reinforced Textile Composites , Richard Douglas Hale
Retrospective Theses and Dissertations
Constant load stress rupture tests were performed on alloy 908. The test matrix used varied oxygen concentration, applied load, temperature, and percent cold work. The effect of modifying surface residual stresses on intergranular oxidation and cracking was examined using constant strain Cring tests;The mechanism for high temperature intergranular fracture in alloy 908 is stress assisted intergranular oxidation cracking. A direct correlation between percent intergranular fracture and oxygen concentration was observed. This result was comparable to the oxidation assisted, intergranular fracture behavior of alloy 718. Internal oxidation, for temperatures at or near 650∘ C and under an applied tensile stress ...
Synthesis Of Launch Vehicle Design And Trajectory Optimization, Veena Savithri Dorairajan
Synthesis Of Launch Vehicle Design And Trajectory Optimization, Veena Savithri Dorairajan
Retrospective Theses and Dissertations
http://www.worldcat.org/oclc/32804161