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Linear Stability Of Non-Parallel Flow In The Entrance Region Of Ducts, Francis Chung-Ti Shen

Doctoral Dissertations

"An investigation is made of the linear stability of the developing flow of an incompressible fluid in the entrance region of annular ducts, circular tubes, and parallel-plate channels. Small axisymmetric disturbances for annular duct and tube flows and small two-dimensional disturbances for channel flow are considered in the analysis. In formulating the stability problems, account is taken of the transverse velocity component of the mainflow. This results in the modified Orr-Sommerfeld equations, one for annular duct and tube flows and the other for channel flow. The mainflow velocity fields utilized in the stability analysis are those from the solutions of …

Numerical Simulation Of Heat, Mass, And Momentum Transfer In An Atmospheric Boundary Layer, Darrell W. Pepper

Doctoral Dissertations

"Considerable interest has developed in recent years to understand transport phenomena in thermally stratified boundary layers. More complete knowledge in this field is needed to improve the prediction of the diffusion of air pollutants in the lower atmosphere as well as in forecasting air-water circulation for weather conditions.

The atmospheric boundary layer is modeled using the equations of continuity, momentum, energy, and concentration. Closure of this set of partial differential equations is hindered by the turbulence terms. Using turbulence kinetic energy, the system of equations is closed by internally determining the exchange coefficients of heat, mass, and momentum along with …

Hydrostatic Extrusion Of Waste Glass And Plastic, Subhash Govind Kelkar

Doctoral Dissertations

"Waste glass and waste plastic combine to form a major portion of nonbiodegradable, solid waste. These waste products aggravate the already too serious problem of environmental pollution. Hence, a means is sought of utilizing this waste in the construction industry, thus solving two problems simultaneously - that of beautifying the environment, and of procuring inexpensive building materials.

Extrusion is not an uncommon process as far as the manufacture of original products is concerned. Hydrostatic extrusion is a modification of the process wherein a billet or slug of some material is forced to flow through a die under the influence of …

Methods For Predicting The Influence Of Intense Sound, Steady Flow, And Elevated Temperature On The Acoustic Performance Of Automotive Exhaust System Components, Richard Chuka Oboka

Doctoral Dissertations

"The principal objective of this investigation was to study the feasibility of developing laboratory techniques for automobile-exhaust muffler design in order to reduce the amount of on-vehicle trial-and-error testing currently required. The investigation included (1) improving the capability of existing laboratory equipment to simulate the conditions in automobile exhaust (i.e., high-amplitude pressure waves, steady flow, and elevated temperature), and (2) theoretical and experimental studies of typical acoustic elements (side-branch resonators, expansion chambers, louvered tubes) used in muffler design. The sound fields used for these studies included pure tones, single pulses (tone bursts), random noise, and simulated automobile exhaust noise.

Empirical …

Transient State Analysis Of Separated Flow Around A Sphere, Ching-Liang Lin

Doctoral Dissertations

"Transient state solution of the Navier Stokes equation was obtained for incompressible flow around a sphere accelerating from zero initial velocity to its terminal free falling velocity. By assuming rotational symmetry around the axis in the falling direction, the Navier Stokes equation and the continuity equation were simplified in terms of vorticity and stream function. The instantaneous acceleration of the falling sphere was calculated by considering the difference between the gravitational force and the drag force in a transient state. The governing partial differential equations were non-dimensionalized. A set of implicit finite difference equations was developed. In order to obtain …

Stability Of The Developing Laminar Flow In A Circular Tube, Lung-Mau Huang

Doctoral Dissertations

"An investigation is made of the linear stability of the developing laminar flow of an incompressible fluid in the entrance region of a circular tube. Both axisymmetric and non-axisymmetric small disturbances are considered in the analysis. The stability characteristics of the fully developed flow are also re-examined. The main flow velocity distribution used in the stability analysis is that from the solution of the linearized momentum equation. The governing equations for the disturbances and the boundary conditions constitute an eigenvalue problem which is solved by a direct numerical integration scheme along with an iteration technique. The solution starts with a …

Rock Fragmentation By Subsurface Thermal Inclusions - A Finite Element Study, Mahendrakumar Ramkrishna Patel

Doctoral Dissertations

"Although rock tunneling machines are being used extensively with performance and cost advantages over traditional drill and blast methods, their usefulness for hard rock excavation is far from being practical due mainly to the inability of present day mechanical cutters to penetrate these rocks economically. Among various novel techniques that are being investigated, internal heating methods seem to be the most promising. This investigation is concerned with a feasibility study of thermal rock fragmentation using heat to create in-depth thermal inclusions.

The three-dimensional problem of in situ rock fragmentation involves parallel rows of equidistant holes drilled to a constant depth. …

The Effects Of High Pressure And Temperature Environments On The Properties Of 6061-T651 Aluminum, Patrick George Davidson

Doctoral Dissertations

"During this experimental testing program the effects of the simultaneous application of high pressure and temperature environments on the mechanical properties of 6061-T651 aluminum were analyzed. From the data obtained at the yield and ultimate points a yield and ultimate model was developed based upon the parameters effective stress, effective strain, and the hydrostatic component of stress. This model was obtained solely from the data acquired from uniaxial tensile specimen tested at various pressures and temperatures. Two other loading paths--biaxial tension and torsion--were then used to verify the accuracy of the model. From the testing program, data were also obtained …

A Study Of The Dynamic Loading Of Hydrodynamically Lubricated Journal Bearings, Nader Khorzad

Doctoral Dissertations

"The analytical and experimental investigation presented here examined the response of a full journal bearing to a unidirectional dynamic load. Frequency response of the bearing at different eccentricity ratios was investigated. It was concluded that the response of the bearing varies with eccentricity. The experimental data obtained was compared to an analytical model which considered inertial, damping, and elastic characteristics of the lubricant film. An investigation of film pressure revealed that the pressure due to journal center acceleration is smaller than the hydrodynamic and squeeze-film pressures"--Abstract, page 1.