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Full-Text Articles in Engineering

Compressible Flow Analysis Of Thrust Augmenting Ejectors, Mohamed Moujahid Dec 1995

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 Dec 1995

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 Bemoulli-Navier hypothesis. The effects of axial and rotary inertia were included in the analysis. The Voigt-Kelvin 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 Oct 1995

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 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 on ...


Buckling Analysis And Optimum Design Of Multidirectionally Stiffened Composite Curved Panel, Navin R. R. Jaunky Oct 1995

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 ...


An Experimental Investigation Of Wall Cooling Effects On Hypersonic Boundary Layer Stability In A Quiet Wind Tunnel, Alan E. Blanchard Oct 1995

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 ...


A Direct Synthesis Method For The Conceptual Design Of Transport Aircraft, Pierre Andre Fruytier Jul 1995

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 step-climb is taken into account. The ...


Numerical Investigation Of Shock-Induced Combustion Past Blunt Projectiles, Jagjit K. Ahuja Jul 1995

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 ...


Dynamic Unstructured Method For Prescribed And Aerodynamically Determined Relative Moving Boundary Problems, Kamakhya Prasad Singh Jul 1995

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 ...


Dynamic Simulation Of General Aviation Cabin Environments And Occupant Restraint Systems, Mark A. Shilladay May 1995

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 ...


Advanced Rover Chassis, Eric Alan Poulson, Collin Lewis, Todd Graves May 1995

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 ...


Standardized Checklists Versus Variable Checklist: An Evaluation In A Light Twin Simulator, Veronica Terese Cote Apr 1995

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 Self-Organizing Map, Weldon Paul Thornton Apr 1995

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

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 ...


Numerical Investigation Of Second-Order Effects In A Supersonic Boundary-Layer, Timothy R. Membrino Apr 1995

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

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 ...


An Experimental Study Of Transient Flows In Pulse Combustors, Michael P. Femandes Apr 1995

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 Boundary-Layer Control, Jacob Kimball Apr 1995

A Computer Model For Airfoils With Moving Surface Boundary-Layer 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 boundary-layer 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 Apr 1995

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 ...


Aerodynamic Design Optimization With Consistently Discrete Sensitivity Derivatives Via The Incremental Iterative Method, Vamshi M. Korivi Apr 1995

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 Apr 1995

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 ...


Nonlinear Analysis Of Composite Beams Under Random Excitations, Snorri Gudmundsson Mar 1995

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 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 ...


Parallel Surface Reconstruction Through Virtual Milling , Kumaran Kalyanasundaram Jan 1995

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 three-dimensional 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 Computer-Aided Design (CAD) descriptions do not exist, though, for objects ...


Adaptive Nonlinear Attitude Control Of Spacecraft , Cheng Tang Jan 1995

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 linear-quadratic 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 Six-Degree-Of-Freedom High Angle-Of-Attack Aircraft Models , Jen-Nai Chou Jan 1995

Optimal Turning Maneuvers For Six-Degree-Of-Freedom High Angle-Of-Attack Aircraft Models , Jen-Nai Chou

Retrospective Theses and Dissertations

Various Minimum-Time Turning Maneuvers for two high angle-of-attack, six-degree-of-freedom, aircraft models have been investigated. The primary aircraft model is for a nonlinear 6-DOF F-16 fighter aircraft with high angle-of-attack maneuverability. The other model is for a linearized 6-DOF F-18 fighter which also can be flown in the high angle-of-attack range. Standard 6-DOF 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 Three-Dimensional Flows On Parallel Computers , Thomas Hans Ramin Jan 1995

Unstructured Grid Algorithms For Two- And Three-Dimensional Flows On Parallel Computers , Thomas Hans Ramin

Retrospective Theses and Dissertations

The Navier-Stokes equations are solved numerically for two-and three-dimensional 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 finite-volume 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 two-dimensional 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 , Wen-Ping Wang Jan 1995

Coupled Compressible And Incompressible Finite Volume Formulations For The Large Eddy Simulation Of Turbulent Flow With And Without Heat Transfer , Wen-Ping Wang

Retrospective Theses and Dissertations

A coupled finite volume approach for solving the time-dependent Navier-Stokes equations is developed for application to the large eddy simulation (LES) of turbulent flow. The preconditioning strategy of coupling the incompressible N-S 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 two-dimensional laminar flows and three-dimensional 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 ...


Unstructured Surface And Volume Decimation Of Tessellated Domains , Kevin Joseph Renze Jan 1995

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 n-dimensional tessellation, not on ...


A Compliant Model For Estimation And Optimization Of Damping In Vibrating Structures , Thomas Jeffrey Thompson Jan 1995

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 Multi-Directionally Reinforced Textile Composites , Richard Douglas Hale Jan 1995

Ultrasonic Nondestructive Evaluation Techniques And The Effects Of Fiber Architecture On Mechanical Performance In Multi-Directionally 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 C-ring 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 Jan 1995

Synthesis Of Launch Vehicle Design And Trajectory Optimization, Veena Savithri Dorairajan

Retrospective Theses and Dissertations

http://www.worldcat.org/oclc/32804161


Turbulent Scalar Transport Using Two-Point Statistical Closure Theory , Robert Charles Sanderson Jan 1995

Turbulent Scalar Transport Using Two-Point 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 ...


Numerical Investigation Of Type Ii Non-Newtonian De/Anti-Icing Fluid Effects On Take-Off Performance For General Aviation Aircraft , Dennis James Cronin Jan 1995

Numerical Investigation Of Type Ii Non-Newtonian De/Anti-Icing Fluid Effects On Take-Off 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 40-50 civil accidents a year according to one account. More viscous than Type I fluids, Type II fluids are inherently non-linear in their shear stress-rate of strain relationship having smaller relative viscosity at higher shear rates. The non-linearity makes properly scaled wind-tunnel 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 take-off maneuvers for general aviation. The method is tested on a two-dimensional NACA 0012 airfoil under typical take-off simulation ...