ETDs: Virginia Tech Electronic Theses and Dissertations

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Virginia Tech has been a world leader in electronic theses and dissertation initiatives for more than 20 years. On January 1, 1997, Virginia Tech was the first university to require electronic submission of theses and dissertations (ETDs). Ever since then, Virginia Tech graduate students have been able to prepare, submit, review, and publish their theses and dissertations online and to append digital media such as images, data, audio, and video.

University Libraries staff are currently digitizing thousands of pre-1997 theses and dissertations and loading them into VTechWorks. Most of these theses and dissertations are fully available to the public, but we will, in general, honor requests by the item's author to restrict access to Virginia Tech only. See our process for Requesting that Material be Amended or Removed.

To search all Virginia Tech print and digital theses and dissertations, use the University Libraries ETD resource guide.

Materials that are restricted to Virginia Tech only may be requested via your own university or public library's Interlibrary Loan program or through the VTechWorks request form that appears when you try to access the item. You might also be able to obtain a copy of the work through ProQuest's database of theses and dissertations. If you are on a Virginia Tech campus but are unable to find the pre-1997 thesis or dissertation you are seeking in VTechWorks, you may also be able to order a physical copy from library storage. Please check the library catalog at http://www.lib.vt.edu/ for physical copies.

The guidelines that apply to Virginia Tech's graduate students as ETD authors can be found at http://guides.lib.vt.edu/ETDguide.

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Now showing 1 - 15 of 15

Aerodynamic characteristics of a hemisphere at hypersonic speeds
Pritchard, Edgar Brian (Virginia Polytechnic Institute, 1959)
Analysis of pressure data obtained at transonic speeds on a thin low-aspect-ratio cambered delta wing-body combination
Mugler, John P. (Virginia Polytechnic Institute, 1958)
An investigation was conducted in the Langley 8-foot transonic tunnels to determine the aerodynamic loading characteristics of a thin conical cambered low-aspect-ratio delta wing in combination with a basic body and a body indented symmetrically for a Mach number of 1.2 in accordance with the supersonic area rule. The tests were conducted at Mach numbers from 0.60 to 1.12 and at 1.43 and at angles of attack generally from -4° to 20°. The wing vas conically cambered over the outboard 15 percent of each semispan. The wing had an aspect ratio of 2.31, 60° sweepback of the leading edge, and had NACA 65A003 airfoil sections parallel to the model plane of symmetry over the uncambered portion. The results of this investigation indicate that a leading-edge separation vortex forms at moderate angles of attack and causes the shape of the span load distribution to change markedly. Significant center of pressure movements are noted at transonic speeds. Indenting the body in accordance with the supersonic area rule had little effect on the aerodynamic loading characteristics. Comparisons with expert mental data for a similar plane wing indicates that the cambered wing is considerably more effective than the plane wing in utilizing the leading edge suction forces to produce thrust. A comparison between experimental and theoretical results indicates fair agreement around sonic speeds.
An analytical method for predicting lift and drag characteristics of flat-top wing-body combinations at supersonic speeds
Hasson, Dennis Francis (Virginia Polytechnic Institute, 1958)
An analysis was presented for predicting lift and drag characteristics of flat-top wing-body combinations at supersonic speeds. These combinations consist of a wing mounted above an expanding body with their apexes being coincident. The assumptions with which the analysis was made are the following: 1. The linear theory was applicable. 2. The leading edge or the wing was coincident or ahead of the body shock. 3. Condition of zero base drag (static pressure at the base equal to the stream static pressure). The analysis was carried out by considering the individual terms which appear in the lift-drag relations separately, and utilizing the most recent theoretical methods to determine them. The analysis was applied to two flat-top wing-body combinations; namely, a semiconical body with an arrow planform wing, and a 3/4 power semibody with a diamond planform wing. For these combinations a free-stream Mach number of 3.35 satisfied the condition for the wing leading edge and the body bow shock to be coincident. To obtain a check on the analysis, the results were compared with experimental data at a Mach number of 3.35.
Calculation of the wave drag due to lift for an arbitrary rectilinear-planform wing-body combination
Olstad, Walter B. (Virginia Polytechnic Institute, 1958)
no abstract provided by author
Design and calibration of a high temperature continuous run electric arc wind tunnel
Grossmann, William (Virginia Tech, 1961-04-15)
The purpose of this thesis project was to design, construct and evaluate the performance of a high temperature continuous-run electric arc wind tunnel. A pilot model of such a facility was designed assuming that equilibrium air was the working gas. The pilot model facility was constructed and consisted of the following components; arc chamber, stagnation chamber, nozzle section, test and diffusor sections. In the arc chamber, the air passes through the positive column of an electric arc there-by raising its stagnation temperature before entering the stagnation chamber. Also included in the design and construction were water cooling and waste disposal systems, air supply and vacuum systems, and electric arc power supply system and control. An examination of tests performed in the electric-arc facility showed that a low density supersonic flow with a stagnation temperature of approximately 10,000 F could be produced. The power level for this flow was 36 kw; however, with an expected increase of power to 72 kw the stagnation temperature should be raised to 15,000 F. Since no valid technique for measuring temperatures of this magnitude has been perfected to the author's knowledge, these temperatures were calculated according to a method as outlined in the present thesis. The present facility will present an opportunity for study in such topic areas as (1) Aerodynamic Ablation, (2) Magnetoaerodynamic studies and (3) Qualitative studies of chemically reacting gas flows.
Design and tests of a six-stage axial-flow compressor having a tip speed of 550 feet per second and a flat operating characteristic at constant speed
Maynard, John W. Jr (Virginia Polytechnic Institute, 1958)
A six-stage axial-flow compressor with a 550 feet per second tip speed and a flat operating characteristic (constant stagnation-pressure ratio at constant speed over the operating range of the compressor) was designed and tested. The design theory and test results are presented in this thesis. It was designed for a constant power input per pound of flow regardless of mass flow. The design specific weight flow was 21.1 pounds per second per square foot of frontal area with an atmospheric discharge at an overall stagnation-pressure ratio of 3.25 and an inlet hub-tip radius ratio of 0.7. In order to reach design conditions the blade setting angles were reset and the machining notches at the root of the first three rotor blades were filled. In an attempt to increase the flat operating range of the compressor, the blade setting angles of the first two stages were increased and those of the last two stages were decreased. Also, the solidity of the first rotor was decreased.
Effect of aerodynamics on the perturbations of a space vehicle orbit
Mayo, Alton Parker (Virginia Polytechnic Institute, 1961)
The present study was undertaken to determine the effects of the aerodynamics on a close earth orbit and reentry trajectory. The aerodynamic influence is compared to the effects of the earth’s oblateness, the sun, and the moon. In order to obtain maximum accuracy and computational speed Encke’s perturbative procedures were used during orbital periods and Cowell’s integration procedures during thrust and reentry periods.
The effect of heat insulation on the cooling requirements of the internal structure of high-speed vehicles
Perkins, John Noble (Virginia Polytechnic Institute, 1958)
The present thesis project consisted of two parts. First, a general method for determining the transient skin temperatures of bodies during high-speed flight was developed. The governing differential equation was presented for this purpose, giving the fundamental relations between the transient skin temperature and flight history. The determination of all pertinent parameters in the equation was discussed, and the Runge-Kutta numerical method of integration was used to obtain the solution. The method was employed to compute the time history of the skin temperatures for several hypothetical flight plans, and the results presented in the form of graphs. For the Mach number and altitude range investigated, the maximum skin temperature obtained was approximately 2200 °R and was found to be largely independent of the type of trajectory. The second portion of the project consisted of determining the effect of heat insulation on the cooling requirements of the internal structure of a high-speed vehicle. The governing equation for heat conduction through an isotropic solid was developed, and then modified to account for nonhomogeneous materials. The initial and boundary conditions for the governing equation were specified, and the equation solved by the method of finite-differences. The temperatures obtained, the first portion the thesis, were used as the outer surface temperature variation of the insulation, and the time history of the inner surface temperature of the insulation (for several thicknesses) was calculated. To make the problem as general as possible, the results were presented in terms of the thermal diffusivity of the insulating material. For illustrative purposes, an example problem was worked using rock wool as the insulating material. It was found that, by using one-half inch of this insulating material, the maximum temperature obtained by the internal structure was less that 5 percent of the skin temperature. Thus, it was concluded that the increase of the temperature of the internal structure of a high-speed vehicle during a limited time of flight, can be held to structurally permissable values by the use of heat insulation placed between the skin and the internal structure of the vehicle.
Effect of tip-speed ratio on induced velocities near a lifting rotor
Heyson, Harry H. (Virginia Polytechnic Institute, 1958)
A theoretical investigation of the asymmetry of induced flow in the vicinity of a lifting rotor in forward flight has been conducted. The analysis is based upon an asymmetric wake which is a logical extension of that used for previous investigations. Equations for the induced velocities at an arbitrary point in space are presented in a form suitable for numerical integration. Numerical results for the normal induced velocity in the lateral plane of the rotor are presented in the form of tables and charts. Comparison with previously available measurements indicates an improvement in accuracy over older theories. The results should be useful in estimating the interference between wing and rotor of compound helicopters and convertiplanes. In addition the results should be applicable to the problem of mutual interference between rotors of multi-rotor helicopters.
Experimental investigation and theoretical considerations of boundary layer transition of the hemisphere at low wall-to-stagnation temperature ratios
Mayo, Edward E. (Virginia Polytechnic Institute, 1959)
The present investigation was undertaken to determine experimentally whether or not instability of the laminar boundary layer on blunt convex bodies exists when the wall-to-stagnation temperature is lowered. It was found that instability existed and theoretical considerations are given to the transition being associated with the formation of ice on the model surface and with an increase in roughness Reynolds numbers due to thinning of the laminar boundary layer at low wall-to-stagnation temperature ratios. The experimental tests were conducted on two-inch diameter spheres at M = 4.95 and free-stream Reynolds numbers per foot of approximately 72. 5 x 10⁶ or 12.1 x 10⁶ based on the model base diameter. Data were obtained tor both the hot wall and cold wall case. The stagnation temperature was approximately 400° F. Initial model wall temperatures were 97°F, for the hot wall test and -320° F for the cold wall tests.
Investigation of the effect of velocity diagram parameters on inlet total-pressure distortions through single-stage subsonic axial-flow compressors
Ashby, George C. (Virginia Tech, 1957-05-15)
A preliminary theoretical and experimental investigation of the effect of velocity diagram parameters on inlet total-pressure distortions through a single-stage subsonic axial-flow compressor for incompressible flow has been conducted. The wake of 1/4-inch diameter rod, measured both upstream and downstream of a rotor, has been compared for various velocity diagrams. The measured downstream wake was also compared with the downstream wake estimated by using a derived equation subject to the assumption that (a) the undistorted and distorted flows enter the rotor with the same absolute direction, (b) the static pressures of the undistorted and distorted flows are equal at the inlet and also at the exit of the rotor, (c) the increase of blade angle of attack in the distorted flow is not sufficient to cause blade stall, and (d) the distorted flow is turned in the rotor passage to the same exit direction, relative to the rotor, as the undistorted flow.>
A method of estimating the apogee and perigee error incurred in establishing the orbit of a spin-stabilized vehicle
Garland, Benjamine J. (Virginia Tech, 1960-06-15)
A theory has been developed which determines the influence of primary errors upon the dispersion of the apogee and perigee altitudes of the orbit of a satellite vehicle. It is seen that the apogee and perigee altitudes are influenced chiefly by the errors in velocity and flight-path angle at burnout of the next-to-last stage, guidance, velocity increment and thrust alinement, and pitching rate at ignition of the last stage. The theory will allow the probability of a satellite vehicle successfully obtaining a given orbit to be determined. A series of charts which greatly reduce the amount of work required in applying the theory are included. The theory has been applied to the Scout missile for a range of injection altitudes and one payload weight which is representative of the capability of this vehicle. One of the major requirements of any future satellite vehicle will be an improved guidance system so that the Scout probably will be the worst case to which the theory will be applied.
The prediction of aerodynamic force and moment coefficients on elliptic cone bodies at both angle of attack and sideslip by use of Newtonian impact theory
Wells, William R. (Virginia Tech, 1961-05-05)
Newtonian theory was applied, in this analysis, to the elliptic cone segment at angles of attack and sideslip. Closed form expressions for the aerodynamic coefficients and static stability derivatives were obtained. Expressions for the full and half conic bodies were given and approximate expressions were given for the half cone case. The circular cone results were obtained as a special case of the general results. Comparisons of the theoretical calculations with experimental results at hypersonic speeds were made of the aerodynamic coefficients and static derivatives for several conic segments. Generally, good agreement was observed for specified ranges of fineness ratios and angles of attack.
Pressure-temperature boundaries for ideal dissociating and ionizing gases
Harrison, William Pendleton, Jr. (Virginia Tech, 1961-04-05)
The problem of determining thermodynamic properties of gaseous systems in which real-gas effects must be considered can be greatly simplified through use of existing ideal-gas theories for the processes of dissociation and ionization. Since, however, the ideal dissociating gas theory neglects ionization effects and the ideal ionizing gas theory does not take into account dissociation, an additional assumption must be made in order to use these two theories within a single system experiencing both effects. The added assumption which is made is that the processes of dissociation, single ionization, and higher levels of ionization all occur independently of one another though in a definite order within the system. With this linearizing assumption of independent gas processes the ideal gas theories then can be applied within their respective ranges of application in order to calculate the thermodynamic properties of any system under equilibrium conditions, provided the ranges of application can be determined. Neither the ideal dissociating gas theory nor the ideal ionizing gas theory explicitly defines the pressure-temperature region throughout which the theory is applicable. In the present work an analytic expression is developed which gives the limiting temperature as a function of pressure for the ideal dissociating gas theory. The method is then generalized in the ionization range so as to provide pressure-temperature boundaries for all levels of ionization within the assumption of independent first-level, second-level, and higher-level ionization processes.
A theoretical and experimental investigation of the annular jet ground effect machine
Graham, William Alexander (Virginia Polytechnic Institute, 1960)
In this work the infrared absorption of neutron irradiated silicon was compared to that of non-irradiated silicon at room and liquid nitrogen temperatures. It was found that instead of the 1.75 micron absorption band that has been mentioned in numerous papers transmission was completely cut off below about 2.5 microns at room temperature and about 1.8 microns at liquid nitrogen temperature. A weak absorption band was noted at 4.4 microns for all three samples at liquid nitrogen temperature and the two irradiated samples at room temperature. Absorption due to free carriers depressed at the longer wavelengths (10-15 microns) with irradiation and cooling as was expected from past experiments. The resistivity of Si₄ increased from an assumed initial value of 10³ ohm-om to 1.89 x 10⁵ ohm-om.

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