Engineering Commons^™

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 …

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 …

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 …

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 …

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 …

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 …

The Analysis Of A Subsonic Jet Issuing Perpendicular To A Freestream Flow From A Flat Plate And A Body Of Revolution, Donald R. Haberman

Mechanical & Aerospace Engineering Theses & Dissertations

An investigation was undertaken to determine the nature of the pressure region around a jet issuing perpendicular to a free stream flow from a flat plate and a cylindrical surface, and to determine the forces which resulted from such a pressure region. It was also attempted to develop an empirical relation to enable the prediction of surface pressure regions from known physical parameters.

The jet was exhausted from a 0.375 inch nozzle perpendicular to a free stream flow of about 90 ft./sec. The flow rate of the jet was then varied to give three free stream to jet velocity ratios …

An Experimental Investigation Of The Vortex Sink Rate Sensors, Nelson L. Lu

Mechanical & Aerospace Engineering Theses & Dissertations

The vortex sink rate sensor device consists basically of an ideal sink flow between two coaxial disks. A sink tube was located at the center of one disk. The vortex was created by the rotation of the unit about its axis of symmetry. Five inch and 10 inch diameter of porous couplers were used for the air chamber here in this investigation. Several slenderness parameters, i.e., the ratio of the sink tube diameter to the height of the air chamber ^ro/n were conducted. Two probes were used to measure the static pressure and stagnation pressure respectively at various positions …

A Theoretical And Experimental Study Of An Unsteady Pressure Measuring System, Ramesh R. Batki

Mechanical & Aerospace Engineering Theses & Dissertations

Experiments were performed to determine the frequency response of gas filled instrument tubes, and the results were correlated with a theoretical model. The theoretical model developed by Bergh and Tijdeman for a series connection of thin circular tubes and volumes was studied in full detail and employed. A measuring system was designed and built to measure pressure ratio and phase lag employing thin nylon or vinyl tubes and strain gage transducers. 1'leasurements were performed using cathode ray tube, strip chart, analog techniques and also a commercial electronic function analyzer and the various results were compared. The theoretical and experimental influence …

Static And Dynamic Buckling Of Shallow Arches, David D. Loendorf

Civil & Environmental Engineering Theses & Dissertations

The static and dynamic buckling behaviors of a shallow, simply supported sinusoidal arch subjected to both a uniformly distributed step pressure load and a purely impulsive load are considered. Five equilibrium paths are obtained for the arch under static loading conditions. Critical static loads corresponding to two different instability modes and based on characteristics in the load displacement curve are obtained numerically. Critical dynamic loads, corresponding to three different instability modes, are obtained from a numerical procedure in which buckling criteria are based on characteristics in the time response of the structure. The influence of damping on the various dynamic …

A Numerical Solution To The Problem Of Rotation Near The Ground, David D. Chen

Mechanical & Aerospace Engineering Theses & Dissertations

No abstract.

Grain Size Reconnaissance Of The Virginia-North Carolina Inner Shelf Analysis By Settling Technique, Robert Bailey Sanford Jr.

OES Theses and Dissertations

The 2-fold purpose of this study is to calibrate a Rapid Sediment Analyzer and to use it to aid in the determination of the genesis of sediment on the inner continental shelf between Cape Henry and Cape Hatteras. Rapid Sediment Analyzer calibration was conducted by comparison of sieving and settling results of similar sands.

The study area was divided into sediment provinces by both a qualitative procedure (grain size and topography) and a quantitatively procedure (factor-vector analysis). Qualitative provinces are beach and surf, upper shore face, lower shore face, sea floor, and terminal shoals. The berm fines from each terminal …

A Study Of Elasto-Viscous Material Under Moving Rigid Wheel, Sou-Nan Wang

Civil & Environmental Engineering Theses & Dissertations

This thesis is considered as the solution of interaction between aircraft wheel and soil under landing of airplane. After treating soil as elasto-viscous material, we get a set of non-linear differential equations, such as momentum equations, in viscous region.

A numerical method, Marker-and·-Cell (MAC) method, was used to solve these equations. All data and curves are obtained by using CDC 6600 computer.

An Experimental Study Of Lateral Soil Pressures And Moments On Flexible Sheet Piles, James H. Donahue

Civil & Environmental Engineering Theses & Dissertations

In order to study the effect compaction has on lateral earth pressures exerted on and bending moments in steel sheet pile bulkheads, an experimental study was undertaken which employed the placement of a non-cohesive soil at two specific densities against three model piles of varying thicknesses. The soil was placed both in a loose and a dense state and the bending strains and deflections of the sheet piles were measured at various stages of backfill. Surface loadings were then placed after completion of the backfilling to observe the effects these loads had on the bending moments. The results of the …