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1995

Aerospace Engineering

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Articles 1 - 30 of 52

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 ...


Improved Periodic Spectral Analysis With Application To Diesel Vibration Data, Peter J. Sherman, Lang B. White Dec 1995

Improved Periodic Spectral Analysis With Application To Diesel Vibration Data, Peter J. Sherman, Lang B. White

Aerospace Engineering Publications

The purpose of this work is to begin the development of a comprehensive time/frequency spectral analysis approach that can be applied to complex signals associated with real world systems, such as rotating machinery. Rotating machinery operating at nominally constant speed comprise a large class of important real world systems that have received relatively little attention in terms of stochastic characterizations of any greater sophistication than those associated with wide sense stationary processes. In this work, a periodic-time/frequency characterization procedure is introduced in the context of vibration analysis associated with a diesel engine operating at nominally constant speed. This ...


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 ...


Flightlines, Vol. 4, No. 1, Jeffrey A. Johnson Oct 1995

Flightlines, Vol. 4, No. 1, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.


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 ...


Numerical Simulations Of Shelterbelt Effects On Wind Direction, Hao Wang, Eugene S. Takle Oct 1995

Numerical Simulations Of Shelterbelt Effects On Wind Direction, Hao Wang, Eugene S. Takle

Geological and Atmospheric Sciences Publications

A neutral boundary layer nonhydrostatic numerical model is used to determine the characteristics of shelterbelt effects on mean wind direction and to study the processing causing wind rotation when air passes through a shelterbelt. The model uses a turbulence scheme that includes prognostic equations for turbulence kinetic energy and a master length scale proposed by Mellor and Yamada. The simulated results are in quantitative agreement with Nord's field measurements. The spatial variation of wind rotation and its dependence on incident angle and shelterbelt porosity is analysed. Dynamic processes of the wind rotation and its interactions with drag force and ...


Identifying Periodic Components In Atmospheric Data Using A Family Of Minimum Variance Spectral Estimators, Christopher Kim Wikle, Peter J. Sherman, Tsing-Chang Chen Oct 1995

Identifying Periodic Components In Atmospheric Data Using A Family Of Minimum Variance Spectral Estimators, Christopher Kim Wikle, Peter J. Sherman, Tsing-Chang Chen

Aerospace Engineering Publications

This work describes the application of a recently developed signal processing technique for identifying periodic components in the presence of unknown colored noise. Specifically, the application of this technique to the identification of strongly periodic components in meteorological time series is examined. The technique is based on the unique convergence properties of the family of minimum variance (MV) spectral estimators. The MV convergence methodology and computational procedures are described and are illustrated with a theoretical example. The utility of this method to atmospheric signals is demonstrated with a 26-year (1964-1989) time series of 70-mb wind components at Truk Islands in ...


Enzothrust Testo Booster, Wanxmkkfsfrs Wanxmkkfsfrs Sep 1995

Enzothrust Testo Booster, Wanxmkkfsfrs Wanxmkkfsfrs

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Simulation Of Temperature Variation In Parachute Inflation, D. K. Chaturvedi Sep 1995

Simulation Of Temperature Variation In Parachute Inflation, D. K. Chaturvedi

D. K. Chaturvedi Dr.

In this paper, the variation of temperature during parachute inflation is simulated by system dynamics methodology. In this methodology, causal loops for system have been identified and flow diagram is drawn. Flow diagram consists of flow rate variables, level variables and auxiliary variables. In causal mechanism principal feedback loops are identified. It also simplfies illustration due to various influencing factors such as pressure, rate of pressure, mass of parachute, textile characteristics, motion of folded parachute to compresion under pressure and interaction between parachute and its container/bag.


Boundary Element Solutions To Wave Scattering By Surface Irregularities On A Fluid-Solid Interface, S. Shenoy, Thomas J. Rudolphi, F. J. Rizzo Jul 1995

Boundary Element Solutions To Wave Scattering By Surface Irregularities On A Fluid-Solid Interface, S. Shenoy, Thomas J. Rudolphi, F. J. Rizzo

Aerospace Engineering Conference Papers, Presentations and Posters

The boundary element method is used to solve fluid-solid half-space problems with fluid-filled dimples and air bubbles on the solid surface. The problems, formulated in the Fourier (frequency) domain, are described by the fullspace three-dimensional acoustic and elastodynamic boundary integral equations (BIE), with pressure and displacement serving as primary variables. The techniques developed are general and may be with any kind of incident wave, however, plane waves are used in all numerical experiments. The equations governing the acoustic region are first converted mathematically to equations like those of an elastic region. The two regions are coupled and solved for the ...


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 ...


A Unified Topological Approach To Electromagnetic Environmental Effects Protection, George H. Baker, J. Philip Castillo, Edward F. Vance Jun 1995

A Unified Topological Approach To Electromagnetic Environmental Effects Protection, George H. Baker, J. Philip Castillo, Edward F. Vance

George H Baker

The presentation recommends an approach for unifying electronic system protection designs for a wide spectrum of electromagnetic environments. A general electromagnetic topological construct is developed as the basis for a consistent shielding and terminal protection methodology. Spectral characteristics of multiple interfering electromagnetic sources, both internal and external, are described. Effects addressed include EMI/EMC, lightning, nuclear EMP, and RF weapons. Protection practices for individual effects are discussed and means for integrating these into a single protection topology.


Supersonic, Turbulent Flow Computation And Drag Optimization For Axisymmetric Afterbodies, Russell M. Cummings, H. T. Yang, Y. H. Oh May 1995

Supersonic, Turbulent Flow Computation And Drag Optimization For Axisymmetric Afterbodies, Russell M. Cummings, H. T. Yang, Y. H. Oh

Aerospace Engineering

The compressible, turbulent flow about an axisymmetric body was numerically studied using the MacCormack unsplit explicit algorithm applied to the mass-average Navier-Stokes equations solved in conjunction with the k-ε turbulence model of Jones and Launder. Numerical predictions of total body drag (pressure drag, skin friction drag, and base drag) were made for an axisymmetric body six diameters in length, with and without a boattail. Surface pressures and viscous layer profiles are compared with available wind tunnel data and are found to be in good agreement for both geometries. The Golden Section optimization method was used to optimize the body ...


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 ...


Vibration Analysis Of A Split Path Gearbox, Timothy L. Krantz, Majid Rashidi May 1995

Vibration Analysis Of A Split Path Gearbox, Timothy L. Krantz, Majid Rashidi

Scholarship Collection

Split path gearboxes can be attractive alternatives to the common planetary designs for rotorcraft, but because they have seem little use, they are relatively high risk designs. To help reduce the risk of fielding a rotorcraft with a split path gearbox, the vibration and dynamic characteristics of such a gearbox were studied. A mathematical model was developed by using the Lagrangian method, and it was applied to study the effect of three design variables on the natural frequencies and vibration energy of the gearbox. The first design variable, shaft angle, had little influence on the natural frequencies. The second variable ...


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 ...


Magnetostrictive Vibration Generation System, Alison B. Flatau, David Hall Apr 1995

Magnetostrictive Vibration Generation System, Alison B. Flatau, David Hall

Iowa State University Patents

A shaker with a Terfenol-D rod actuator includes a mass coupled to both ends of the rod through a spring seat, a spring seat/adjuster and a spring washer. The actuator is mounted inside a cylindrical coil, which in turn is mounted inside a cylindrical permanent magnet, which in turn is mounted inside a cylindrical housing. An electrical drive system provides a predetermined excitation signal to the coil to cause the rod to vibrate under the influence of the magnetic field generated by the coil. One embodiment features a vibrating mass on one end of the rod. An implantable shaker ...


Flightlines, Vol. 3, No. 2, Jeffrey A. Johnson Apr 1995

Flightlines, Vol. 3, No. 2, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.


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 ...


Gps Modeling For Designing Aerospace Vehicle Navigation Systems, John J. Dougherty, Hossny El-Sherief, Daniel J. Simon, Gary A. Whitmer Apr 1995

Gps Modeling For Designing Aerospace Vehicle Navigation Systems, John J. Dougherty, Hossny El-Sherief, Daniel J. Simon, Gary A. Whitmer

Electrical Engineering & Computer Science Faculty Publications

The complexity of the design of a Global Positioning System (GPS) user segment, as well as the performance demanded of the components, depends on user requirements such as total navigation accuracy. Other factors, for instance the expected satellite/vehicle geometry or the accuracy of an accompanying inertial navigation system can also affect the user segment design. Models of GPS measurements are used to predict user segment performance at various levels. Design curves are developed which illustrate the relationship between user requirements, the user segment design, and component performance.


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 ...