Engineering Commons^™

Analysis Of Moisture Absorption And Diffusion In Fiber Reinforced Polymeric Resin-Matrix Composite Materials, Stephen Stern Tompkins

Mechanical & Aerospace Engineering Theses & Dissertations

The diffusion of moisture through fiber reinforced polymeric-matrix composite materials has been studied analytically. The diffusion in the orthotropic, nonhomogeneous material was modeled, in detail, with a two-dimensional transient diffusion analysis. An effective diffusivity for the composite was determined in terms of the fiber volume fraction and the resin diffusivity. This effective diffusivity is in better agreement with recent data than those previously determined using less complex models.

The influence of both material and environmental parameters on the moisture content of the composite was determined analytically. Predicted moisture contents were compared over a wide range of values for emittance, solar …

Studies Of Fracture And Deformed Surfaces Of High Strength Aluminum Alloys By X-Ray Diffraction, Tamma K. Kumar

Mechanical & Aerospace Engineering Theses & Dissertations

X-ray observations of fatigue fracture and deformed surfaces of 7075-T6 aluminum were conducted in this study. The (111) and (222) diffraction peaks were obtained from the fractured and deformed surfaces. It was observed that in comparison with the base metal, the fracture exhibited line broadening similar to that due to cold working. The broadening is indicative of plastic deformation in the vicinity of the advancing crack tip during the fracture process. Also the different regions of fracture exhibited varying degrees of line broadening. With respect to the fatigue crack, the slow crack growth region showed a greater broadening, and, hence, …

Optimal Control Of A Large Space Telescope Using An Annular Momentum Control Device, Arun Anant Nadkarni

Mechanical & Aerospace Engineering Theses & Dissertations

Application of a new development in the field of momentum storage devices, the Annular Momentum Control Device (AMCD), to the twin problems of large angle maneuvers and fine pointing control is considered. The basic concept of the AMCD consists of a spinning rim, with no central hub area, suspended by a minimum of three magnetic bearings, and driven by a noncontacting electromagnetic spin motor. The dissertation considers in detail the design of an optimal controller to achieve both large angle maneuvers and the fine pointing control of a Large Telescope (LST) with a single configuration, consisting of a single AMCD …

Static Temperature Measurements In Supersonic Flow Using Lasar Raman Spectroscopy, Paul A. Nystrom

Mechanical & Aerospace Engineering Theses & Dissertations

Laser Raman spectroscopy is a nonintrusive technique which can generate mean static temperature (MST) data within flow fields. By ratioing two simultaneously gathered portions of the Raman scattered spectrum, absolute intensity measurements were not needed. This method was applied to a supersonic cold air jet, where the NST ranged from 160'K to 300'K. Accurate measurements were not realized due to the presence of flow contaminates, especially water vapor.

Evaluation Of Hydrogen As A Cryogenic Wind Tunnel Test Gas, Richard Carl Haut Ii

Mechanical & Aerospace Engineering Theses & Dissertations

A theoretical analysis of the properties of hydrogen has been made to determine the suitability of hydrogen as a cryogenic wind tunnel test gas. By using Cryogenic hydrogen, instead of air or cryogenic nitrogen, as the wind tunnel test gas, a significant increase in the test Reynolds number may be achieved without increasing the aerodynamic loads. Under sonic conditions, for example, compared to air at ambient temperature, cryogenic hydrogen at a pressure of one atmosphere produces an increase in Reynolds number of a factor of approximately fourteen while cryogenic nitrogen, at the same pressure, produces an increase of only a …

Fundamental Analysis Of The Linear Multiple Regression Technique For Quantification Of Water Quality Parameters From Remote Sensing Data, Charles Henry Whitlock Iii

Civil & Environmental Engineering Theses & Dissertations

Inconsistent results have been obtained from previous experiments which have applied linear multiple regression techniques to remote sensing data for quantification of water quality parameters. The objective of this investigation is to define optical physics and/or environmental conditions under which the linear multiple regression should be applicable. To achieve this objective, an investigation of the signal response equations is conducted and the concept is tested by application to both analytical test cases and actual remote sensing data from a laboratory under controlled conditions.

Investigation of the signed response equations shows that the exact solution for a number of optical physics …

Precise Frequency Control Of The Voltage Controlled Oscillator Using Finite Digital Word Lengths, Timothy Peter Hulick

Electrical & Computer Engineering Theses & Dissertations

For an oscillator that is periodically swept in frequency between some upper and lower bound, the output amplitude may easily be made constant and therefore known with a high degree of certainty. The instantaneous frequency exists only at a point in time and therefore possesses a zero probability of existing at any point. This thesis deals with the development of a method for interchanging the probability density functions of amplitude and frequency so that the latter becomes known with certainty while the former is known only to the extent that it is within a certain range.

The method developed makes …

A Model To Investigate The Influence Of Suspended Sediment On The Mass Transport Of A Pollutant In Open Channel Flow, Raymond Scott Chapman

Civil & Environmental Engineering Theses & Dissertations

The environmental impact of the transport of pollutants in open channel flow has for many years been of interest due to the continuous introduction of heavy metals, pesticides, herbicides, and other foreign substances into natural waterways. In order to fully understand this transport process, it-is necessary to examine the significance of its individual components. In the present study an explicit two-dimensional finite difference model, designed to investigate the influence of suspended sediment on the pollutant transport process, is presented. Specific attention is directed toward examining the role of suspended sediment in 1) the turbulent vertical transport mechanism in a stratified …

Effect Of Compliant Wall Motion On Turbulent Boundary Layers, Dennis M. Bushness, Jerry N. Hefner, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

A critical analysis of available compliant wall data which indicated drag reduction under turbulent boundary layers is presented. Detailed structural dynamic calculations suggest that the surfaces responded in a resonant, rather than a compliant, manner. Alternate explanations are given for drag reductions observed in two classes of experiments: (1) flexible pipe flows and (2) water-backed membranes in air. Analysis indicates that the wall motion for the remaining data is typified by short wavelengths in agreement with the requirements of a possible compliant wall drag reduction mechanism recently suggested by Langley. Copyright © 1977 American Institute of Physics.

Evaluation Of Upwelling Infrared Radiance In A Nonhomogeneous Nonequilibrium Atmosphere, Sundaresa Venkata Subramanian

Mechanical & Aerospace Engineering Theses & Dissertations

The primary purpose of this study was to investigate the influence of vibrational nonequilibrium upon upwelling infrared radiance from the earth's atmosphere. Basic equations are presented for calculating the atmospheric transmittance, heating rates, and equilibrium and nonequilibrium upwelling radiances. By employing the Lorentz line-by-line model for spectral absorption, heating rates and upwelling radiances were calculated for equilibrium as well ·as nonequilibrium conditions in the spectral range of 4.6 μ CO and 3.3 μ 'CH₄ bands. For the spectral range of CO fundamental band, the influence of different 1~arameters on the upwelling radiance was also investigated. The results indicate that …

Similitude Of Mass Transfer Processes In Distorted Froude Model Of An Estuary, Carvel Hall Blair

Mechanical & Aerospace Engineering Theses & Dissertations

The project began with the design and construction of a hydraulic Froude model of the Lafayette River, a small well mixed estuary in Norfolk, Virginia. Horizontal scale is 1/540, vertical scale 1/12 yielding a vertical distortion of 45. Adjustment by roughness strips and screens produced close agreement of model-prototype tide heights, currents, and salinities in the deep reaches comprising 80% of the estuary volume. Some scale effect in velocity and tide height could not be eliminated in the shallow upper branches of the estuary, probably because of the high geometric distortion and the narrowness of the channel at kilometer 6.7. …

An Efficient Dft Algorithm Using The Walsh Transform, Albert P. Gerheim

Electrical & Computer Engineering Theses & Dissertations

The matrix transformation relating the sequency and frequency domains is derived. It is shown that these­ frequency-to-frequency conversion can be performed via a computationally efficient sparse matrix algorithm. The sequency-to-frequency algorithm can be used with a fast Hadamard transform to implement a discrete Fourier trans­ form. The efficiencies of this combined algorithm and a radix-two fast Fourier transform are compared.

The algorithm is applied to the sequency domain de­ sign of a Wiener digital filter. Improved computational efficiencies are achieved relative to the procedure de­veloped by Kahveci and Hall (9).

An Engineering Solution To Improve Water Quality In A Tidal Lagoon, Richard Warren Price

Civil & Environmental Engineering Theses & Dissertations

Rising demand for better water quality stimulated research and development of ways to improve the quality level in existing as well as proposed water systems. At present, most of the solutions focus on biological and chemical processes.

Many natural or man-made water bodies act as receivers for both point and non-point pollution sources. Employment of biological and chemical treatment has proved successful in many of these cases; however, in some cases a more natural physical solution of an engineering mode would be more desirable. A "flushing" technique using the tidal fluctuation as a driving force has been investigated and the …

The Synthesis Of New Maleimide Addition Polymer Precursors, Richard B. Brown

Chemistry & Biochemistry Theses & Dissertations

1H-2,3-dimethylpyrrolo(1,2-a) benzimidazol-l-one (27) and 1H,9H- 2,3,7,8-tetramethyl-bispyrrolo(1,2-a:6,7-a')benzodiimidazo1-1,9-dione (32) have been synthesized from dimethylmaleic anhydride and o-phenylenediamine and 1,2,4,5-tetraaminobenzene, respectively. The presence of reactive olefinic double bonds in the synthesized compounds was of interest as a site for possible addition polymerization.

The synthetic route involved, in both cases, a simple nucleophilic substitution reaction between the diamine(or tetraamine) and the anhydride to form an intermediate amide-acid-amine which rapidly cyclized to the imide amine. The final ring closure required more rigorous conditions and occurred at melt reaction temperatures.

Analysis Of Spread Multi-Jet Vtol Aircraft In Hover, Leroy F. Albang

Mechanical & Aerospace Engineering Theses & Dissertations

An investigation of VTOL aircraft lift losses in hover has been conducted to evaluate a method for a simplified test technique. Three flat plate models were tested to determine their usefulness in predicting hover characteristics by comparing results between plate and three­ dimensional models. Attempts to correlate the out of ground effect results for the plate models with the empirical expression for calculating jet-induced loads were successful for the models which used engine simulators producing efflux characteristics similar to the three­ dimensional model engines. Data for the model using engine simulators with characteristics unlike those of the three-dimensional model simulators …

A Method For Improving The Accuracy In Phase Change Heat Transfer Data Through Increased Precision In Thermophysical Property Determinations, John Philip Drummond

Mechanical & Aerospace Engineering Theses & Dissertations

Wind tunnel model materials typically have thermophysical properties that vary with both position and temperature. A numerical study using a finite difference representation of the heat conduction equation has been performed on several of these model materials to determine their thermal response under a specified heat loading. This study has confirmed the feasibility of using an effective thermophysical property to account for the existence of variable thermal properties when a model undergoes aero­ dynamic heating. The effective property, when used in the reduction of phase-change heat transfer data, forced agreement of the actual transient behavior of a model with the …

Effect Of Rod Gap Spacing On A Suction Panel For Laminar Flow And Noise Control In Supersonic Wind Tunnels, William D. Harvey

Mechanical & Aerospace Engineering Theses & Dissertations

It has been well established that the test section flow of conventional supersonic and hypersonic wind tunnels contains significant levels of disturbances. These disturbances are mainly caused by the radiation of aerodynamic noise from the turbulent boundary layer on the nozzle walls. This noise level has been shown to have an important effect on boundary layer transition measured on models in tunnels. The purpose of this thesis is to present results of a coordinated experimental and theoretical study of a sound shield concept which aims to provide a means of noise reduction in .the test section of supersonic wind tunnels …

An Experimental Investigation Of A Cold Jet With Solid Centerbody Emitting From A Flat Plate Into A Subsonic Free Stream, Danny K. Livingston

Mechanical & Aerospace Engineering Theses & Dissertations

A study of the influence of a solid center body on lift loss and pitching moment has been conducted. It has been well established that a round free jet emitted from a flat plate at right angles to a cross flow causes an induced pressure distribution on the plate which adversely affects the lift and pitching stability of the flat plate.

This investigation has employed a 2.58 - cm diameter round jet with a 1.91 - cm diameter solid rounded core in order to modify the induced flow field and attempt to reduce the lift loss and pitching moment. Preliminary …

Application Of Boundary Layer Theory To Suction Through Streamwise Slots In Wind Tunnel Walls, Michael Harold Berger

Mechanical & Aerospace Engineering Theses & Dissertations

A theoretical investigation at Mach 6 and 8 has been conducted on a model of a wind tunnel sound shield. The flat plate model consists of interchangeable circular and wedge shaped longitudinal rods with gaps between the rods for boundary layer removal. One­ dimensional gas dynamics results have been applied to model the pressure distribution for the array of cylinders. Comparisons with experimental pressure distributions and numerical potential flow solutions indicate good agreement. It has been demonstrated that stagnation line heat transfer can be accurately predicted for laminar and-turbulent flow for circular cylinders. The flow around the wedge rods was …

The Effect Of Unreinforced Cutouts On The Buckling Of Thin Conical Shells Loaded By Central Axial Compression, Garla Arjuna

Mechanical & Aerospace Engineering Theses & Dissertations

Analytical trends for the linear bifurcation buckling of thin isotropic right-circular-conical shells with unreinforced cutouts are investigated. Clamped, constant-thickness conical shells with homogeneous, isotropical material properties are analyzed for uniform axial compression. The buck­ ling loads are obtained by the use of the STAGS (Structural Analysis of General Shells) computer program which is based on a finite difference numerical approach. Variables defining the geometry of the cutout and the cone are nondimensionalized and the relationship between the nondimensional buckling load and nondimensional cutout parameter is established. A range of the cutout sizes is investigated for which linear bifurcation buckling results …

Dynamics Of Explosion Remnants In Earth-Orbits, Joseph T. Fuss

Mechanical & Aerospace Engineering Theses & Dissertations

Explosions in space produce particles that are hazardous to space vehicles. Some of these particles are not trackable and their locations must be predicted by dynamical methods.

This investigation sheds light on three different, areas, First, ignoring perturbations, the characteristics of a three dimensional envelope outlined by the sum of individual particle orbits is determined, Second, the distribution of the particles is found as a function of time, Finally, the movement, of the body via secular perturbations is investigated. Magnitudes of the explosion, the point of. detonation in the parent satellite's orbit, and the radius of perigee of the parent …

An Experimental And Theoretical Study Of The Flow Phenomena Within A Vortex Sink Rate Sensor, Dashrath Khodidas Patel

Mechanical & Aerospace Engineering Theses & Dissertations

The objective of this investigation was to obtain a detailed description of the flow field within a vortex sink rate sensor and to observe the influence of viscous effects on its performance.

The sensor basically consists of a vortex chamber and a sink tube. The vortex chamber consists of two circular coaxial disks held apart, at their periphery, by a porous coupling. One circular disk has an opening to permit the mounting of the sink tube, in such a manner that the vortex chamber as well as the sink tube have a common axis of rotation.

Air was supplied radially …

A Finite Element Analysis Of Unsymmetrically Laminated Rectangular Plates, Stanley F. C. Tseng

Mechanical & Aerospace Engineering Theses & Dissertations

The behavior of laminated plates with coupled extension-bending was investigated using the finite element method. A stiffness matrix for a rectangular element with 20 degrees of freedom was developed using a symbolic mathematics interpreter program. A finite element analysis program was written for the analysis of flat plate. Results i for plate deformations and internal moment distributions are compared with existing exact solutions or experimental data and excellent agreement is obtained.

The Design And Performance Of A Fiber Optic Pressure Transducer, Raymond Henry Pahler Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

Design and performance characteristics of a fiber optic pressure transducer are presented and discussed. The transducer consists of a cylindrical metal housing with a specular reflecting aluminum diaphragm at the distal end and a circular array of fiber optic light guides at the proximal end. The center bundle is connected to a light source with the surrounding bundles carrying reflected light to a photodetector. A change in pressure on the diaphragm causes a deflection which in turn causes a change in intensity over the light receiving fibers. The intensity is converted to a voltage signal by the photodetector circuit. Thus, …

Electroplating, James G. Farrell

OTS Master's Level Projects & Papers

Electrometallurgical industries comprise an important segment of the world's manufacture of metal products. These industries involve three major categories: electrowinnowing, electrorefining and electroplating. Electrowinnowing consists of purifying raw ore to a relatively pure metal by electrolysis. Extraction of aluminum from bauxite is an example. Electrorefining involves electrolysis of metallic solutions to recover or produce extremely pure metal. Recovery of precious metals is often done by electrorefining. Electroplating involves the coating of one metal or object with another metal for various reasons. The chief reasons are the protection of a part from corrosion or its beautification. Another type of electroplating is …

An Investigation Of A Free Jet At Low Reynolds Numbers, George C. Greene

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis presents a comparison of the measured and calculated flow field properties of a nozzle of unusual design which was used to produce an incompressible, low Reynolds number ]et. The "nozzle" is essentially a porous metal plate which covers the end. of a pipe. Results are presented for nozzle Reynolds numbers from 50 to 1000 with velocities of 100 or 200 ft/sec. The nozzle produces s, uniform velocity profile at nozzle Reynolds numbers well below those at, which conventional contoured nozzles are completely filled with the boundary layer. A Jet mixing analysis based on the boundary layer equations accurately …

Computer-Aided Design Of Light Aircraft To Meet Certain Aerodynamic And Structural Requirements, Joanne Lynn Walsh

Mechanical & Aerospace Engineering Theses & Dissertations

Nonlinear mathematical programming techniques are applied to a particular aircraft design problem, that of determining the maximum range design for light aircraft subject to certain aerodynamic and structural requirements. Search techniques available in an existing nonlinear optimization computer program, AESOP, are applied to the design problem. Seven design variables are used to define the wing dimensions, the wing skin thickness, the cruise velocity, the amount of fuel carried, and the engine horsepower. The influence of different design requirements on the range is observed and discussed.

Numerical Study Of The Turbulent Boundary Layer In A Hypersonic Nozzle, Joan Patricia Gosink

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical study of the turbulent boundary layer in a hypersonic nozzle is presented. The boundary layer equations are solved by a second order, implicit finite difference scheme developed at Langley Research Center. The technique is applicable to laminar, transitional or turbulent compressible or incompressible boundary layer flows for planar or axisymmetric geometries. A technique is presented for utilizing experimental data to start the finite difference solution.

Turbulent boundary-layer measurements on axisymmetric nozzle walls at Mach number 6 are presented and compared with numerical predictions obtained by starting the solution in the stagnation chamber and from a downstream experimental station. …

Commentary On And Extension Of Calculative Procedure For Co2 Production, Ralph M. Rotty

Mechanical & Aerospace Engineering Faculty Publications

Further refinements are made in the method of calculating amounts of carbon dioxide released to the atmosphere through the combustion of fossil fuels. Data available in the UN Statistical Yearbook are used as the basic sources rather than the summary, World Energy Supplies, U.N. Statistical Papers, Series J because the most recent data are available several months earlier in the yearbook and because data are included for natural gasoline, natural gas liquids, and cement production. Coal, lignite, crude petroleum, “marketed” natural gas, flared natural gas, and cement are itemized separately and revised CO₂ emission estimates are made for …

A Numerical Technique For Solving Rigid Body Impact On An Incompressible, Viscous Medium, Cecil Thomas Chapman

Civil & Environmental Engineering Theses & Dissertations

A technique for solving rigid-body impact on a viscous, incompressible medium is presented. The numerical scheme is adapted from the Marker and Cell (MAC) method developed to solve problems involving time-dependent motion of a viscous, incompressible fluid in two-dimensional space. As the pressure end velocity fields are computed throughout the flow field, the solution gives the force and displacement time history of the rigid-body during the impact phase. In conjunction with this, through a system of marker particles, the changes in configuration of the viscous medium on impact can be studied. With a "movie frame" (incremental time) approach, computational experimentation …