Engineering Commons^™

Thermodynamic And System Performance Analysis Of A Heat Pump That Employs A Two-Phase Flow Collector As Evaporator, Yu-Fang Chiang

Mechanical & Aerospace Engineering Theses & Dissertations

A thermodynamic model is developed to analyze the thermal performance of two phase flow solar collectors, The well-known equilibrium homogeneous theory is used to model the two phase flow in the solar collectors. The resultant set of coupled ordinary differential equations for saturated pressure and quality of working fluids in the collector tubes are solved by an iterative procedure using a fourth order Runge-Kutta method. The results are then applied to determine the thermal performance of a solar assisted heat pump which uses two phase flow collector as the evaporator, The results indicate that even with the use of less …

Experimental Study Of Delta Wing Leading-Edge Devices For Drag Reduction At High Lift, Thomas Dwight Johnson Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

Future fighter aircraft requirements specify efficient supersonic cruise and high-g maneuverability at high lift. The slender delta wing meets the first requirement but has large lift induced drag increments at high lift. One method to alleviate the drag is to control the flow at the wing leading edge (LE) by means of small LE devices, so as to maintain locally attached flow to higher angles of attack and thus increase the level of aerodynamic thrust.

The devices selected for evaluation were the fence, slot, pylon-type vortex generator (VG), and sharp leading-edge extension (SLEE). These devices were tested on a 60° …

A Nonlinear Hybrid Vortex Method For Wings Having Side-Edge Separations, Li-Chuan Chu

Mechanical & Aerospace Engineering Theses & Dissertations

A Nonlinear Hybrid-Vortex method (NHV-method) has been developed for predicting the aerodynamic characteristics of wings exhibiting side-edge separations. The present method is a coupline between vortex-panel and vortex-line methods. In the near-field calculations, vortex panels are used while in the far-field calculat1ons, vortex lines are used.

The wing and its free-shear layers are divided into planar quadrilateral panels having first-order vorticity distribution. The aerodynamic boundary conditions and continuity of the vorticity distributions are imposed at certain nodal points on the panels. An iterative technique is used to satisfy these conditions to obtain the vorticity distributions and the wake shape as …

Feasibility Of Quasi-Random Band Model In Evaluating Atmospheric Radiance, Navin Mirakhur

Mechanical & Aerospace Engineering Theses & Dissertations

The use of the quasi-random band model in evaluating the upwelling atmospheric radiation is investigated. The spectral transmittance and total band absorptance are evaluated for selected molecular bands by using the line-by-line model, quasi-random band model, exponential sum fit method, and empirical correlations, and these are compared with the available experimental results. The atmospheric transmittance and up­ welling radiance have been calculated by using the line-by-line and quasi-random models and are compared with the results of an existing program called LOWTRAN. The results obtained by the exponential sum fit and empirical relations are not in good agreement with experimental results …

Natural Convection In Shallow Inclined Enclosures, Effendy Arif

Mechanical & Aerospace Engineering Theses & Dissertations

A two dimensional natural convective flow in a shallow inclined enclosure has been considered. A mathematical model has been developed to simulate the flow. The system of governing equations has been solved using finite-differencing techniques and the alternating direction implicit method.

The effect of the Raleigh number, the enclosure aspect ratio and orientation on the heat transfer and flow development have been studied by determining the Nusselt numbers and analyzing a number of contour maps of temperature and stream function fields, and velocity profiles. The Nusselt number has been found to increase with the Raleigh number, the enclosure aspect ratio, …

Eigensystem Assignment Using Singular Value Decomposition, Ronald Dean Alley

Electrical & Computer Engineering Theses & Dissertations

An interactive approach to computer-based control system design is formulated and presented. There are four key features to this approach. Singular value decomposition is used for several matrix operations, rather than Gaussian methods, for improved numerical accuracy. Dynamic memory allocation is implemented to reduce system core requirements for matrix storage. Interactive plant parameter modification is implemented to allow user interaction with the program~ reducing design time. Finally, disk input-output is minimized to increase response time.

This design system is demonstrated in examples in which distinct user specified eigenvalues are achieved, and eigenvectors close to a user specified set of eigenvectors~ …

An Apparatus For Measuring The Thermal Conductivity Of Cast Insulation Materials, Christine A. Wilkins, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

A steady-state apparatus has been developed for measuring the thermal conductivity of cast materials. The design has employed a novel thermal symmetry arrangement which can permit total electrical isolation of the test material from its surroundings. © 1980 American Institute of Physics

Analytic And Experimental Studies Of A True Airspeed Sensor, Joseph Yao-Cheng Shen

Mechanical & Aerospace Engineering Theses & Dissertations

The objective of this study was to analyze and design a true airspeed sensor which will replace the conventional pitot-static pressure transducer. This sensor should have the following characteristics: the flow phenomenon is vortex procession, or the "vortex whistle", it should have no moving parts, and also is to be independent of temperature, density, altitude or humidity changes. This sensor has been designed mainly for small commercial aircraft with the airspeed up to 321.9 km/hr (200 mph).

In an attempt to model the complicated fluid mechanics of the vortex precession, three-dimensional, inviscid, unsteady, incompressible fluid flow was studied by using …

A Dimensionality Reduction Algorithm For The Karhunen Loeve Transform, Salomi T. Charalambous

Computational Modeling & Simulation Engineering Theses & Dissertations

The Karhunen Loeve Transform has conclusively been shown to be the optimum data compression algorithm for signals belonging to the same second order stationary process. Consequently, researchers have been searching for a fast implementation for the transform. Fast imple­mentation methods similar to those developed for other orthogonal transforms are generally not applicable to the Karhunen Loeve Transform (KLT). Also, since the basis vectors composing the transformation matrix of the KLT are the eigenvectors of the covariance matrix of the input process, they must be computed first. The research re­ ported here is an attempt to reduce the dimensionality of the …

Influence Of Nonequilibrium Radiation And Shape Change On The Flowfield Of A Jupiter Probe With Ablation And Mass Injection, Sundaresa Venkata Subramanian

Mechanical & Aerospace Engineering Theses & Dissertations

The influence of nonequilibrium radiative energy transfer and the effect of probe configuration changes on the flow phenomena around a Jovian entry body is investigated. The radiating shock-layer flow is assumed to be axisymmetric, viscous, laminar and in chemical equilibrium. The radiative transfer equations are derived under nonequilibrium conditions which include multi-level energy transitions. The equilibrium radiative transfer is calculated with an existing nongray radiation model which accounts for molecular band, atomic line and continuum transitions. The nonequilibrium results are obtained with and without ablation injection in the shock layer. The nonequilibrium results are found to be influenced greatly by …

The Development Of A Stepped Frequency Microwave Radiometer And Its Application To Remote Sensing Of The Earth, Richard Forrest Harrington

Electrical & Computer Engineering Theses & Dissertations

The design, development, application, and capabilities of a variable frequency microwave radiometer are described. This radiometer has demonstrated the versatility, accuracy, and stability required to provide contributions to the geophysical understanding of ocean and ice processes. The design technique utilized a closed-loop feedback method, whereby noise pulses were added to the received electromagnetic radiation to achieve a null balance in a Dicke switched radiometer. Stability was achieved through the use of a constant temperature enclosure around the low loss microwave front end. The Dicke reference temperature was maintained to an absolute accuracy of 0.1 K using a closed-loop proportional temperature …

The Significance Of Peel Stresses In Cyclic Debonding, Richard A. Everett Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

One of the possible failure modes in adhesively bonded joints is cyclic debonding -- progressive separation of the adherends by cyclic failure of the adhesive bond. In this study cyclic debonding in an adhesively bonded crack-lap shear specimen has been investigated by means of a linear elastic finite-element analysis and a series of constant­ amplitude axial fatigue tests. The primary purpose of this study was to test the hypothesis that cyclic debonding is due largely to tensile peel stresses in the adhesive.

The results of this study have indicated that not all of the tensile peel stresses in the adhesive …

Finite Element Model Of A Timoshenko Beam With Structural Damping, Louis Ablen Roussos

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical integration technique, a modified version of the Newmark method, is applied to transient motion problems of systems with mass, stiffness, and small nonlinear damping. The nonlinearity is cast as a pseudo-force to avoid repeated recalculation and decomposition of the effective stiffness matrix; thus, the solution technique is dubbed the "pseudo-force Newmark method." Comparisons with exact and perturbation solutions in single-degree-of-freedom problems and with a Gear-method numerical solution in a cantilevered Timoshenko beam finite element problem show the solution technique to be efficient, accurate, and, thus, feasible provided the nonlinear damping is small. As a preliminary step into the …

Luminescence In Slipped And Dislocation-Free Laser-Annealed Silicon, R.H. Uebbing, P. Wagner, H. Baumgart, H. J. Queisser

Electrical & Computer Engineering Faculty Publications

Photoluminescence of cw laser-annealed silicon shows a dramatic difference in electronic behavior of the reconstructed material depending upon either creation or suppression of dislocations. Beyond a critical exposure time slip appears, and the luminescence of these samples is dominated by dislocation-related defect levels.

Curing And Flow Of Thermosetting Resins For Composite Materials Pultrusion, Howard L. Price Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

Fibrous composite materials for mechanical and structural applications often are expensive due to high labor costs. One economical way of making composites is pultrusion, a manufacturing process in which resin-impregnated fibers are pulled at a constant speed through a heated die which shapes the resin-fiber mass and cures the resin. Most of the work which has been done on the process has been of an empirical nature, with limited understanding of the process principles. Most of the experience with pultrusion has been gained with polyester resins and glass fibers. Very little experience has been gained with higher performance, more costly …

Stable Equilibrium Statistical States For Spheromaks, George Vahala, Linda L. Vahala

Electrical & Computer Engineering Faculty Publications

Incompressible nondissipative magnetohydrodynamic turbulence is treated for spherical systems. From the absolute equilibrium expectation values of the fields one can investigate those initially quiescent states for which no large mean square velocity will develop. This stable state is force-free and gives rise to the Hill vortex structure for the magnetic flux surfaces.

Effect Of Precursor Heating On Radiating And Chemically Reacting Viscous Flow Around A Jovian Entry Body, Kuo Yen Szema

Mechanical & Aerospace Engineering Theses & Dissertations

The influence of changes in the precursor region flow properties (resulting from absorption of the radiation from the shock layer) on the entire shock layer flow phenomena around a Jovian entry body is investigated under physically realistic conditions. In the precursor region, the flow is considered to be inviscid and the variations in flow properties are determined by employing the small perturbation technique as well as the thin layer approximation. The flow in the shock layer is assumed to be steady, axisymmetric and viscous. The analysis is carried out by considering both the chemical equilibrium and nonequilibrium composition of the …

Inviscid Two-Dimensional Vortex-Panel Method For Calculating The Pressure Distribution Over Noncircular Cylinders At Various Flow Incidence Angles, Sophia Kokkinos Ashley

Mechanical & Aerospace Engineering Theses & Dissertations

A method. has been implemented to calculate the potential flow pressure distribution over noncircular cylinders at various flow incidence angles. The inviscid, solution has been obtained by replacing the surface of a noncircular cylinder with a vortex sheet. The surface has been approximated by a number of flat panels. Each vortex panel has been assumed to have a constant vorticity, and the condition of no-circulation applied.. Solutions yield the local tangential velocity and pressure coefficient at each point.

The accuracy of the method has 'been established through comparison of the predicted results with existing exact theoretical results.

Comparisons of the …

Design, Calibration, And Application Of A Sensor For Measuring Time Dependent Angle Of Attack Of Helicopter Blades, Weiyuan Henry Liu

Mechanical & Aerospace Engineering Theses & Dissertations

Various pressure probes were designed and tested which could be attached to helicopter blades when a helicopter is in flight. The pressure probes consisted of spherical heads which were held in place by cylindrical shanks. Built inside the heads were transducers to measure the pressure differential between pressure ports which were located on the front portion of the spherical head facing the airstream. Data was obtained over a range of airstream velocity of 11,6 to 88.4- m/s (38 to 290 ft/sec), corresponding to Reynolds numbers of 0.24 to 1.84x10⁵ based on the sphere diameter. Both static and dynamic tests …

An Experimental Investigation Of A Turbulent Boundary Layer With Suction Through Closely Spaced Streamwise Slots, Stephen P. Wilkinson

Mechanical & Aerospace Engineering Theses & Dissertations

The object of this research was to experimentally evaluate a suction surface for use with incompressible turbulent boundary layers. The surface consisted of an array of closely spaced slots aligned in the direction of the free stream flow. Direct drag and mean boundary layer velocity profile measurements showed that the slotted surface had nominally the same suction characteristics as the porous surface.

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, …

Temperature And Time Dependent Viscosity Of An Elastomer Modified Epoxy Resin, Woodrow Williard Wagner Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

Temperature effects on the viiscosity of an epoxy resin (diglycidyl ether of bisphenol A - DGEBA), an elastomer (carboxy terminated butadiene acrylonitrile - CTBN), and two blends containing nominally 10 percent elastomer were examined from strain rates of 0.1 sec^-1 to 10,000 sec-¹ over a temperature range from 300K to 450K. All results indicated the greatest drop in viscosity occurred for each of the materials over the temperature range of 300K to 350K. In addition, the materials exhibited Newtonian responses over the entire strain rate range, Adding small amounts of elastomer to the I epoxy only moderately effected …

Crack Propagation In Aluminum Sheets Reinforced With Boron-Epoxy, George Lawrence Roderick

Mechanical & Aerospace Engineering Theses & Dissertations

The literature has shown that crack propagation in cracked metal sheets can be significantly reduced by bonding an uncracked reinforcement to the metal sheet. However, cyclic debonding typically occurs over a localized area near the crack. Herein, an analysis was developed to predict both the crack growth and debond growth in a reinforced system. The analysis was based on the use of complex variable Green's functions for cracked, isotropic sheets and uncracked, orthotropic sheets to calculate inplane and interlaminar stresses, stress intensities and strain-energy-release rates. An iterative solution was developed that used the stress intensities and strain-energy-release rates to predict …

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 …

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 …

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 …

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 …