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Articles 1591 - 1620 of 1700
Full-Text Articles in Mechanical Engineering
Effects Of Blowing Ratio On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Joseph L. Lenertz
Effects Of Blowing Ratio On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Joseph L. Lenertz
Theses and Dissertations
This experiment analyzed the effects of blowing ratio on heat transfer to the throat region of a porous-walled nozzle, using the AFIT low speed shock tube. Heat flux data were taken from both sides of a two-dimensional Mach 2.0 Re-m=5.2x107 nozzle using thin film resistance thermometers. One side was transpiration-cooled by secondary air injection through a sintered wall, while the other side served as a control. Control results were validated using empirical relations, and cooled side results showed up to a 14% reduction in heat transfer coefficient at blowing ratios of only 0.51%. The linear nature of cooling effectiveness …
Binaural Room Simulation, Brian A. Smith
Binaural Room Simulation, Brian A. Smith
Theses and Dissertations
Research in binaural and spatial hearing is of particular interest to the Air Force. Applications in cockpit communication, target recognition, and aircraft navigation are being explored. This thesis examines human auditory localization cues and develops a mathematical model for the transfer function of a sound signal traveling from an isotropic point source through a rectangular room to both ears of a listener. Using this model as a guide, non-head coupled binaural sound signals are generated in a binaural room simulation. Reflection and attenuation cues included in the computer generated signals are varied in order to determine which cues enhance the …
Experimental Investigation Of The Effects Of Blowing Ratio Parameter On Heat Transfer To A Film-Cooled Flat Plate, Marco R. Valencia
Experimental Investigation Of The Effects Of Blowing Ratio Parameter On Heat Transfer To A Film-Cooled Flat Plate, Marco R. Valencia
Theses and Dissertations
The effects of blowing ratio on film cooling effectiveness were investigated. Two round-nosed test plates were used. One made of aluminum and the second of corian (low thermal conductivity). Injection at 35 degrees in the downstream direction was studied. Helium was mixed with air to produce a density ratio (coolant to mainstream) of 1.6 and 2.0, while the blowing ratio varied from 0.3 to 2.2. Surface temperature was measured by thin film gages located up to a nondimensional downstream distance X/D of 30. Two injection regimes, weak and strong, were found. In the weak regime, film cooling reduced gage heat …
Mitigation Of Shock Waves In A Cylindrical Tunnel By Foam, Grant W. Fondaw
Mitigation Of Shock Waves In A Cylindrical Tunnel By Foam, Grant W. Fondaw
Theses and Dissertations
This study investigated the effectiveness of foam linings in mitigating shock waves in tunnels. A polyurethane foam liner of varying density, crush strength and thickness was modeled inside a 1 meter radius tunnel and an explosion of 1.25 kg of plastic explosive was simulated. Using CTH, an Eulerian- Lagrangian hydrodynamics code from Sandia National Laboratories, the overpressures were computed and compared graphically to determine the effect of varying each foam parameter. The walls of the tunnel consisted of a perfectly reflecting boundary, and in some cases, a foam liner. Low density foam provided the most shock attenuation. with a 20 …
Optimal Control And Estimation For Discrete-Time Periodic And Multirate Systems, Vikram Kapila
Optimal Control And Estimation For Discrete-Time Periodic And Multirate Systems, Vikram Kapila
Theses and Dissertations
For linear time-invariant systems it has been shown that the solutions to the optimal reduced-order modeling, estimation, and control problems can be characterized using optimal projection equations, sets of Riccati and Lyapunov equations coupled by terms containing a projection matrix. These equations provide a strong theoretical connection between standard full-order results such as linear-quadratic Gaussian theory and have also proved useful in the comparison of suboptimal reduction methods with optimal reduced-order methods. In addition, the optimal projection equations have been used as the basis for novel homotopy algorithms for reduced-order design. This thesis considers linear periodic plants and develops necessary …
Solving Nonlinear Composite Material Problems Using The Automated Structural Optimization System (Astros), Robert Bolha
Solving Nonlinear Composite Material Problems Using The Automated Structural Optimization System (Astros), Robert Bolha
Theses and Dissertations
Most advanced composite materials have nonlinear stress versus strain curves--grossly so in the laminas shear direction. If linear approximations are used, overly conservative design will result. This thesis expands the usefulness of the Automated Structural Optimization System (ASTROS) finite element (FE) program by incorporating a newly developed capability to include material nonlinearities. By dividing a FE problem into several intervals, and incorporating the changing nature of the nonlinear material properties within each element, a good approximation of the laminate's actual stresses and strains can be obtained without the undue experimentation involved in testing every individual configuration. Each material property is …
Rewet Performance Of A Rectangular Grooved Heat Pipe Wick After Gravitationally Induced Dryout, Lowell S. Hawthorne
Rewet Performance Of A Rectangular Grooved Heat Pipe Wick After Gravitationally Induced Dryout, Lowell S. Hawthorne
Theses and Dissertations
The effects of increased acceleration forces on the transient dryout and rewet performance of an axial groove heat pipe wick were experimentally studied using inclination to simulate increased acceleration forces. Two durations of increased acceleration were investigated, one being less than the time required for the groove to reach steady-state dryout conditions, the other being sufficient to ensure the groove had reached steady-state dryout conditions. The groove's extent of dryout was found to be greater at increased levels of acceleration. The period of time required for the groove to rewet after an acceleration induced dryout increased as acceleration increased. The …
Effect Of Transverse Vibration On The Capillary Limit Of A Wrapped Screen Wick Copper/Water Heat Pipe, Mark C. Charlton
Effect Of Transverse Vibration On The Capillary Limit Of A Wrapped Screen Wick Copper/Water Heat Pipe, Mark C. Charlton
Theses and Dissertations
The effect of transverse vibration on the capillary limit of a copper/water heat pipe with a tightly wrapped screen wick was investigated. The capillary limit was measured over a range of operating temperatures under static conditions. A bench-top shaker was used to provide vibration normal to the longitudinal axis of the pipe, and the capillary limit was measured at vibration frequencies of 30, 250, and 1000 Hz. At each of these frequencies, tests were run at vibration levels of 1.0, 2.5, and 5.0 G. The pipe was maintained at a zero degree inclination angle and power throughput was increased until …
A Study Of Heat Flux Induced Dryout In Capillary Grooves, Timothy J. Murphy
A Study Of Heat Flux Induced Dryout In Capillary Grooves, Timothy J. Murphy
Theses and Dissertations
This is an experimental study of ethanol flowing in the narrow grooves of a copper plate which is subjected to heat fluxes sufficient to evaporate more liquid than can be replaced by capillary pumping. Three groove geometries are used: square, rectangle, and trapezoid. The objective is to simulate aspects of liquid flow in heat pipes with axial grooves. In order to validate analytical models of capillary flow in grooves, the capillary limit, dryout front location, and dryout front movement in response to power draw downs are documented. The results show the rewet performance of the groove is dependent on geometry. …
Passive Damping Of A Solar Array, Mark A. Scharpen
Passive Damping Of A Solar Array, Mark A. Scharpen
Theses and Dissertations
This study was an attempt to conceptualize, design, build, and test a constrained layer damping device that uses mechanical advantage for the purpose of increasing the damping of transient vibration of a five-bay planar truss. The aluminum truss was clamped to a fixed support and simulated a solar array. A conventional constrained layer treatment was designed, built, and tested to serve as a benchmark for comparison. For the conventional treatment, Plunkett and Lee's segmented constraining layer technique was used. The improved device, two three-layer sandwich beams spanning the two bays nearest the built-in end, were supported several inches away from …
Vibration Suppression In Large Flexible Space Structures Using Active Control Techniques, Chad T. Matheson
Vibration Suppression In Large Flexible Space Structures Using Active Control Techniques, Chad T. Matheson
Theses and Dissertations
This report investigates the use of active vibration control techniques applied to the PACOSS Dynamic Test Article as an experimental structure. In the course of the research, a mathematical model of the lightly damped experimental structure was created based on experimental data. This model was used in the design of two classes of controllers. The first class is pure rate feedback of the structure's measured states such that global stability is insured. The second type of controller investigated was an optimal controller (LQG) that was created using the truncated mathematical model. The rate feedback controller showed significant improvements in the …
Baseline Experiments On Coulomb Damping Due To Rotational Slip, John P. Santacroce
Baseline Experiments On Coulomb Damping Due To Rotational Slip, John P. Santacroce
Theses and Dissertations
Two experimental pin-type joint models are developed to study the effects of Coulomb Damping due to rotational slip. Model One is an inverted beam allowed to pivot at one end as a pendulum. Model Two is a horizontally mounted beam allowed to pivot about its center. The equations of motion for the joint geometries, considering only macro-slip friction, are developed and solved. Theoretical and experimental results for the response of the models in vibration are presented showing energy dissipation versus clamping force for the joint(s).
Shock Tube Study Of The Effects Of Large Density Differences And Blowing Ratio On Heat Transfer To A Film-Cooled Flat Plate, Thomas A. Eads
Shock Tube Study Of The Effects Of Large Density Differences And Blowing Ratio On Heat Transfer To A Film-Cooled Flat Plate, Thomas A. Eads
Theses and Dissertations
The effects of coolant-to-mainstream density ratio (D.R.) and mass flux (blowing) ratio (Mb) on flat plate heat transfer were investigated in a shock tube. The round-nosed plate has a single row of holes inclined 35° downstream with two-diameter lateral spacing and hole length of three diameters. Mixing helium with air in the shock tube produced a D.R. range of 1.2 to 2.1. The parameters studied approach those of film-cooled turbine components. For an Mb range of 0.4 to 3 and 10% mainstream turbulence, heat flux was measured with thin-film heat flux gauges located 4 to 30 hole diameters downstream of …
Experimental Feedback Of Fractional Order States Of A Lightly Damped Structure, Robert C. Mccall
Experimental Feedback Of Fractional Order States Of A Lightly Damped Structure, Robert C. Mccall
Theses and Dissertations
The purpose of this study was to investigate the effectiveness of using fractional order time derivatives of position feedback signals in the active control of vibration. To that end, circuitry was built and evaluated that finds the half order derivative of an input signal. The magnitude responses of the fractional derivative circuits is very good, but there are large phase shifts present that may degrade the performance of the controllers. Two methods of incorporating the fractional derivative signals into the controller were examined. One method involved developing a similarity transformation that transforms an integer order state controller into an equivalent …
Transient Heat Transfer Measurements On A Film Cooled Flat Plate In A Shock Tube, Rakhman Gul
Transient Heat Transfer Measurements On A Film Cooled Flat Plate In A Shock Tube, Rakhman Gul
Theses and Dissertations
During this study a simple model of a flat plate was chosen to determine heat flux from a high speed flow behind a shock wave into the film cooled flat plate. An electrical analog was used to convert the output of the heat flux gages into heat flux. Free stream turbulence within the flow behind the shock wave and that generated by a turbulence generator was determined and its effects on the heat transfer data were then studied for comparison with previous experimental work. The thin-film heat flux gages were calibrated and their calibration constants were then used to determine …
Damping Of Layered Beams With Mixed Boundary Conditions, Eugene T. Cottle
Damping Of Layered Beams With Mixed Boundary Conditions, Eugene T. Cottle
Theses and Dissertations
For many years, viscoelastic materials have been used in damping treatments to control vibration. In order to optimize a damping treatment for maximum damping, a design engineer must be able to predict frequencies of vibration of damped normal modes and loss factors as a function of the design parameters. Theoretical models of layered beams have been developed, but to date, exact solutions have assumed boundary conditions to be the same for all layers. In this thesis, equations of motion for a damped, layered beam are solved for the longitudinal displacement of both elastic layers, as well as the lateral displacement …
Flexible Engineering Software: An Integrated Workstation Approach To Finite Element Analysis, Brant Arnold Ross
Flexible Engineering Software: An Integrated Workstation Approach To Finite Element Analysis, Brant Arnold Ross
Theses and Dissertations
One obstacle preventing more engineers from using finite element analysis (FEA) is the difficulty of transferring data between steps in the modeling process. A Fortran computer program, Rosetta.BYU, has been developed to open data paths between finite element preprocessors (mesh generators) and finite element analysis programs, using a custom data structure. It accepts neutral data files, Version 2.0 IGES data files, and Movie.BYU files for input/output. An application of Rosetta is described. A general workstation manager program, Davinci.BYU, is reviewed that provides a support layer between the engineer and the operating system, organizes software and data files, and facilitates on-line …
Solution To Eigenvalue Problems Of Antisymmetric Cross-Ply And Antisymmetric Angle-Ply Laminated Plates Using Affine Transformations, Zaffir A. Chaudry
Solution To Eigenvalue Problems Of Antisymmetric Cross-Ply And Antisymmetric Angle-Ply Laminated Plates Using Affine Transformations, Zaffir A. Chaudry
Theses and Dissertations
Using affine transformations and suitably recasting the buckling vibration differential equations, the eigenvalue problem of anti-symmetric cross-ply and antisymmetric angle-ply laminated rectangular plates has been reduced to a function of two strong material constants, the generalized rigidity ratio, whose range is in the closed interval from 0 to 1, and the ratio of principal lamina stiffness. With the reduction in number of constants an exhaustive parameter study of buckling and vibration solution trends, is possible. The buckling coefficients decrease with decreasing value of generalized rigidity ratio for both antisymmetric cross-ply and antisymmetric angle-ply laminates. For a given aspect ratio, and …
Sensitivity Of Process Variables On Rigid Polyurethane Foaming, Bruce A. Pugsley
Sensitivity Of Process Variables On Rigid Polyurethane Foaming, Bruce A. Pugsley
Theses and Dissertations
Inadequate understanding and/or control of the polyurethane rigid foam process normally requires five to ten percent overpack of cavities to obtain correct fill and foam characteristics. This practice of overpacking has resulted in excessive waste and cost.
An Improved Fission Product Pressure Model For Use In The Venus-Ii Disassembly Code, Ray Leland Jensen
An Improved Fission Product Pressure Model For Use In The Venus-Ii Disassembly Code, Ray Leland Jensen
Theses and Dissertations
The world's growing need for safe, reliable, and long-term energy sources has intensified the research being conducted in the development of nuclear power. The operation of power reactors is contingent upon the continued availability of the fissile material required to maintain a critic a l reactor. The only naturally occuring fissile material is an isotope of uranium, U-235, which only accounts for 0.76 percent of the uranium that is mined. Due to the relative scarcity of this important fissile material it is estimated the United States' sources of economically recoverable fissile material will be delinquished with in about twenty-five years.^1
Steady-State Fluidics: Computer-Aided Analysis Of Analog Fluidic Circuits By Use Of Experimentally Determined Characteristic Curves, Raymond P. Martin Jr.
Steady-State Fluidics: Computer-Aided Analysis Of Analog Fluidic Circuits By Use Of Experimentally Determined Characteristic Curves, Raymond P. Martin Jr.
Theses and Dissertations
One of the fundamental tasks confronting engineers is the transmission and control of energy. The engineer, faced with this requirement and influenced by details of a specific, situation, his education and experience, and the customer's desires, will probably select a mechanical, electrical, or electro-mechanical system. Often a better choice exists—the use of a fluid power system. Fluid power systems employ pressurized fluids, liquids and/or gases, to transmit and control energy. Hydraulic systems use liquids, usually special oils or treated water. Pneumatic. systems use air or other gases. Both types are versatile and find a wide range of application.
Steady State Fluidics: The Static Matching Of Fluidic Amplifiers And Loads, Frank J. Redd
Steady State Fluidics: The Static Matching Of Fluidic Amplifiers And Loads, Frank J. Redd
Theses and Dissertations
"Fluidics" is the title applied to a relatively new technology which is concerned with the control of fluid power and the processing of information through the use of the fluid mechanical properties of the fluid medium itself. The absence of moving parts and the relatively low sensitivity to enviromental conditions suggest the probability that fluidic systems will prove to be faster and more reliable than the mechanically controlled (valves, diaphragms, springs, etc.) fluid systems which they are designed to replace.
Alcohol Assisted Hydrocarbon Fuels: A Comparison Of Exhaust Emissions, Power Output And Fuel Consumption Using Static And Dynamic Engine Test Facilities, Dwight J. Bushnell
Alcohol Assisted Hydrocarbon Fuels: A Comparison Of Exhaust Emissions, Power Output And Fuel Consumption Using Static And Dynamic Engine Test Facilities, Dwight J. Bushnell
Theses and Dissertations
America’s energy crunch— something new for a country that has been used to great affluence. America’s smog— an eye stinging, lung burning situation which the Environmental Protection Agency has "promised" to rectify. These are two outstanding problems that face the engineer and scientist of today. The end of the era of cheap gasoline has brought the beginnings of a quiet revolution to Detroit: an improvement in the efficiency, economy and emission level of the American automobile. Word has penetrated to the automotive engineers that the emissions level, fuel economy and automobile safety are the prime design considerations for the automobile …
Determination Of The Most Economically Feasible Method For High Volume Machining Of A Discharge Port In A Powder-Metal Compressor Cylinder, Perry W. Carter
Determination Of The Most Economically Feasible Method For High Volume Machining Of A Discharge Port In A Powder-Metal Compressor Cylinder, Perry W. Carter
Theses and Dissertations
The purpose of this study was to ascertain the most economically feasible method for high volume machining of a discharge hole in a power metal compressor cylinder.
Transient Convective Heat Transfer In Closed Containers During And After Gas Injection, Jennings Donell Means
Transient Convective Heat Transfer In Closed Containers During And After Gas Injection, Jennings Donell Means
Theses and Dissertations
This dissertation presents experimental data correlations for the spatially - averaged convective heat transfer coefficient for thin walled closed containers during and after gas injection. The different modes of heat transfer were identified, and correlations were made for each. Correlations are presented for the injection period, post-top injection, post-bottom injection, post- tangential, post-radial injection, and post-ejection heat transfer for various tank geometries. Of special significance are the very high heat transfer rates that were shown to be present in some cases immediately after injection. Heat transfer rates were shown to be, for a short period, up to almost two orders …
Analysis Of Heat Generation And Temperature In High Speed, High Temperature Bearing Balls, Hans R. Ringger
Analysis Of Heat Generation And Temperature In High Speed, High Temperature Bearing Balls, Hans R. Ringger
Theses and Dissertations
This thesis reports an investigation of the generation of heat on, and the prediction of temperature of high-speed, dry-film lubricated, stainless steel bearing balls.
The Design And Analysis Of An Electro-Pneumatic Signal Converter, Richard K. Thornton
The Design And Analysis Of An Electro-Pneumatic Signal Converter, Richard K. Thornton
Theses and Dissertations
In the field of process control it is desirable to study dynamic characteristics such as frequency response and distortion when determining just how equipment is to be controlled. Pneumatic controllers, transmitters, control valves, etc., all have dynamic behaviors which can be expressed mathematically as transfer functions. Each component plays an important role in determining the entire system behavior. Frequency response is one technique used in developing a component’s transfer function. By driving a device with a sinusoidal signal of fixed amplitude and frequency the output amplitude and phase shift are measured and compared with that of the input. Varying the …
Finite Conductance Element Method Of Conduction Heat Transfer, E. Clark Lemmon
Finite Conductance Element Method Of Conduction Heat Transfer, E. Clark Lemmon
Theses and Dissertations
One of the basic goals in engineering is to formulate models which will provide a means for analytically predicting observed phenomenon. For some time, the partial differential equations describing the steady state and transient conduction of heat within a solid have been available. However, the straight forward use of these equations is often restricted due to the surface geometry of the solid. If the surface geometry is at all irregular, exact solutions will in general not exist. In that case, a solution is sought by some approximate numerical technique. The two techniques most often used are the finite difference method …
An Aerodynamic Investigation Of The Causes Of Overhead Electrical Transmission Line Gallop, Eric Nathan Skousen
An Aerodynamic Investigation Of The Causes Of Overhead Electrical Transmission Line Gallop, Eric Nathan Skousen
Theses and Dissertations
Overhead electrical transmission lines vibrate due to the action of a prevailing wind. These cable vibrations can be classified into two categories— high-frequency and low-frequency. The high-frequency vibrations, "aeolian" vibrations or "singing wires," is a low-amplitude phenomenon. It has been largely controlled with the use of various mechanical dampers [l, 2],
Measurement And Analysis Of Data In Turbulent And Transition Regions Of Two-Phase Flow, Akula Venkatram
Measurement And Analysis Of Data In Turbulent And Transition Regions Of Two-Phase Flow, Akula Venkatram
Theses and Dissertations
The main aim of the project was to examine the possibility of using the hot wire anemometer to detect particles in a fluid. It was hoped that the presence of the particles would affect the autocorrelation plot and the energy spectrum of the velocities measured in the fluid.