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Full-Text Articles in Engineering
Understanding The Relationship Between Urban Areas And The Boundary Layer Using Remote Sensing Methods, Gabriel A. Rios
Understanding The Relationship Between Urban Areas And The Boundary Layer Using Remote Sensing Methods, Gabriel A. Rios
Dissertations and Theses
The atmospheric boundary layer is crucial to the exchange in energy between the Earth's surface and the atmosphere. Within this layer, the majority of human activities are carried out, which makes understanding the boundary layer especially important for many of our interests. A key component of this energy exchange is found at the surface, was surface properties are the interface through which momentum, heat, moisture, and other fluxes are transferred between media. Not only does the surface act as an interface, but as an actor that influences the exchange efficiency and rates. This concept is the crux of atmospheric boundary …
Shock Wave And Boundary Layer Interaction, Blake Keuchel, Lauren Andrews, Corryn Rahe
Shock Wave And Boundary Layer Interaction, Blake Keuchel, Lauren Andrews, Corryn Rahe
Williams Honors College, Honors Research Projects
Air entering the engine of a supersonic aircraft must be slowed to subsonic speeds for the engine to perform properly and not become significantly damaged over time. Diffusers are designed to create a shockwave to slow down air to subsonic speeds before the air enters the engine. This project will focus on the numerical analysis and design of diffuser geometries for supersonic aircraft engines. The main objective is to evaluate supersonic flow over different geometries, specifically the interaction between shock waves and boundary layer, and to minimize the amount of drag created by different diffuser geometries to optimize the efficiency …
A Study Of Constant Voltage Anemometry Frequency Response, Alex D. Powers
A Study Of Constant Voltage Anemometry Frequency Response, Alex D. Powers
Master's Theses
The development of the constant voltage anemometer (CVA) for the boundary layer data system (BLDS) has been motivated by a need for the explicit autonomous measurement of velocity fluctuations in the boundary layer. The frequency response of a sensor operated by CVA has been studied analytically and experimentally. The thermal lag of the sensor is quantified by a time constant, MCVA. When the time constant is decreased, the half-amplitude cut-off frequency, fCVA, is increased, thereby decreasing the amount of attenuation during measurements. In this thesis, three main approaches have been outlined in theory and tested experimentally …
Development Of An Autonomous Single-Point Calibration For A Constant Voltage Hot-Wire Anemometer, Ryan Murphy
Development Of An Autonomous Single-Point Calibration For A Constant Voltage Hot-Wire Anemometer, Ryan Murphy
Master's Theses
Traditionally, the measurement of turbulence has been conducted using hot-wire anemometry. This thesis presents the implementation of a constant voltage hot-wire anemometer for use with the Boundary Layer Data System (BLDS). A hot-wire calibration apparatus has been developed that is capable of operation inside a vacuum chamber and flow speeds up to 50 m/s. Hot-wires operated with a constant-voltage anemometer (CVA) were calibrated at absolute static pressures down to 26 kPa. A thermal/electrical model for a hot-wire and the CVA circuit successfully predicted the measured CVA output voltage trend at reduced pressure environments; however, better results were obtained when the …
Multi-Row Film Cooling Boundary Layers, Greg Natsui
Multi-Row Film Cooling Boundary Layers, Greg Natsui
Electronic Theses and Dissertations
High fidelity measurements are necessary to validate existing and future turbulence models for the purpose of producing the next generation of more efficient gas turbines. The objective of the present study is to conduct several different measurements of multi-row film cooling arrays in order to better understand the physics involved with injection of coolant through multiple rows of discrete holes into a flat plate turbulent boundary layer. Adiabatic effectiveness distributions are measured for several multi-row film cooling geometries. The geometries are designed with two different hole spacings and two different hole types to yield four total geometries. One of the …
An Analytic Solution Of The Thermal Boundary Layer At The Leading Edge Of A Heated Semi-Infinite Flat Plate Under Forced Uniform Flow, Robert Jessee
An Analytic Solution Of The Thermal Boundary Layer At The Leading Edge Of A Heated Semi-Infinite Flat Plate Under Forced Uniform Flow, Robert Jessee
LSU Master's Theses
Abstract The heated flat plate under uniform flow has been vastly studied, with the Blasius and Pohlhausen solutions developed over 100 years ago. These solutions are numerical in nature. Here, an analytic solution is found for the temperature and velocity profiles at the leading edge of a heated flat plate under forced uniform flow. By defining a similarity variable the governing equations are reduced to a dimensionless equation with an analytic solution at the leading edge. This report gives justification for the similarity variable via scaling analysis, details the process of converting to similarity form, and presents a similarity solution. …
Modeling Two-Phase Flow And Heat Transfer In Polygonal Microchannels, Sai Sashankh Rao
Modeling Two-Phase Flow And Heat Transfer In Polygonal Microchannels, Sai Sashankh Rao
LSU Doctoral Dissertations
Microfluidics is a burgeoning research area with applications ranging from microfluidic cooling to biomolecule synthesis. Here we study two problems to gain an improved understanding of two-phase flow and heat transfer in microfluidic devices. We also study a third problem on boundary layer flow out of theoretical interest. In the first problem, we study the heat and mass transfer in polygonal micro heat pipes under small imposed temperature differences. A micro heat pipe, used in electronics cooling, consists of a closed polygonal microchannel filled with a wetting liquid and a long vapor bubble. We model the evaporation, fluid flow, and …
Mitigation Of Moving Shocks In An Expanding Duct, Veraun Chipman
Mitigation Of Moving Shocks In An Expanding Duct, Veraun Chipman
UNLV Theses, Dissertations, Professional Papers, and Capstones
Inviscid flow theory governs the bulk motion of a gas at some distance away from the walls (i.e. outside the boundary layer). That is to say, there are no viscous forces in the bulk flow, which is modeled using the Euler equations. The Euler equations are simply the Navier-Stokes equations with zero viscosity terms. An ideal inviscid fluid, when brought into contact with a surface or wall, would naturally slip right past it since the fluid has no viscosity. In real life, however, a thin boundary layer forms between the wall or surface and the bulk flow. Shock wave boundary …
Influence Of Approach Flow Conditions On Urban Street Canyon Flow, Karin Blackman
Influence Of Approach Flow Conditions On Urban Street Canyon Flow, Karin Blackman
Electronic Thesis and Dissertation Repository
The turbulent flow within a street canyon and the approaching boundary layer has been studied using idealized wind tunnel models and a semi-idealized field experiment conducted in Nantes, France. The effect of upstream roughness on street canyon flow (lateral length/height, L/h = 30) using either 3D (cube) or 2D (rectangular block) upstream roughness, of the same height as the canyon, has been studied for two streamwise canyon width to height aspect ratios (AR) of 1 and 3 using Particle Image Velocimetry. A further wind tunnel model of equivalent geometry to the field experiment was used to compare with flow data …
Constant Voltage Hot-Wire Anemometry For The Boundary Layer Data System, Hon Yee Li
Constant Voltage Hot-Wire Anemometry For The Boundary Layer Data System, Hon Yee Li
Master's Theses
To continue the development of the Boundary Layer Data System (BLDS), a constant voltage hot-wire anemometer (CVA) is implemented into the BLDS for flight-testing. The hot-wire anemometer was chosen as an alternative to the traditional pressure probe because of the ability to measure both average velocity and fluctuating velocity within the boundary layer. Previous work done on the benchtop has led to the design of miniaturization, flight-capable hardware for the BLDS. The next step in the development of the BLDS – CVA calls for quantifying the accuracy of the boundary layer measurements measured by the CVA system. To do this, …
Microphone-Based Pressure Diagnostics For Boundary Layer Transition, Spencer Everett Lillywhite
Microphone-Based Pressure Diagnostics For Boundary Layer Transition, Spencer Everett Lillywhite
Master's Theses
An experimental investigation of the use low-cost microphones for unsteady total pressure measurement to detect transition from laminar to turbulent boundary layer flow has been conducted. Two small electret condenser microphones, the Knowles FG-23629 and the FG-23742, were used to measure the pressure fluctuations and considered for possible integration with an autonomous boundary layer measurement system. Procedures to determine the microphones’ maximum sound pressure levels and frequency response using an acoustic source provided by a speaker and a reference microphone. These studies showed that both microphones possess a very flat frequency response and that the max SPL of the FG-23629 …
Cfd Simulations For The Effect Of Unsteady Wakes On The Boundary Layer Of A Highly Loaded Low Pressure Turbine Airfoil (L1a), Samuel J. Vinci
Cfd Simulations For The Effect Of Unsteady Wakes On The Boundary Layer Of A Highly Loaded Low Pressure Turbine Airfoil (L1a), Samuel J. Vinci
ETD Archive
The study of a very high lift, low-pressure turbine airfoil in the presence of unsteady wakes was performed computationally and compared against experimental results. The experimental data were collected in a low speed wind tunnel under high (4.9 ) and then low (0.6 ) freestream turbulence intensity conditions on a linear cascade with wakes that were produced from moving rods upstream of the cascade. The flow coefficient was kept at 0.7 while the rod to blade spacing was changed from 1 to 1.6 to 2 blade spacings. These cases were conducted for Reynolds number equal to 25,000 and 50,000, based …
Boundary Layer Data System (Blds) Heating System, John Hauge, Drew Hutcheson, Paul Scott
Boundary Layer Data System (Blds) Heating System, John Hauge, Drew Hutcheson, Paul Scott
Mechanical Engineering
The boundary layer data system (BLDS) is the result of a collaborative effort between Dr. Westphal, a researcher and instructor at Cal Poly, and Northrop Grumman. The BLDS is capable of measuring the boundary layer profile and characteristics of flow over aerodynamic surfaces and is intended for high altitude, high speed use. The instruments inside the BLDS malfunction at the low temperatures present when operating in flight at altitudes above 30,000 ft. To solve this problem, analysis was done on the existing BLDS which determined the heating requirements, around 50 watts, needed to keep the internal temperature within the rated …
Boundary Layer Influences On The Subsonic Near-Wake Of A Family Of Three-Dimensional Bluff Bodies, Charles Willliam Alcorn
Boundary Layer Influences On The Subsonic Near-Wake Of A Family Of Three-Dimensional Bluff Bodies, Charles Willliam Alcorn
Mechanical & Aerospace Engineering Theses & Dissertations
A study is reported on subsonic bluff body near-wake flows. It has been determined that one family of bluff bodies, namely slanted-base ogive cylinders, can experience either a closed recirculating near-wake, or a longitudinal vortex near-wake depending on the base slant-angle and the Reynolds number. This suggests a dependence of near-wake parameters on the state of the boundary layer ahead of separation. This report addresses the influence of the boundary layer on the near-wake of slanted-base bluff bodies. Experiments were conducted in two facilities, the 6-inch Magnetic Suspension and Balance System (MSBS) at NASA Langley Research Center and the Old …
An Experimental Study Of An Axisymmetric Turbulent Boundary Layer Disturbed By A Periodic Freestream, Chithrabhanu Koodalattupuram
An Experimental Study Of An Axisymmetric Turbulent Boundary Layer Disturbed By A Periodic Freestream, Chithrabhanu Koodalattupuram
Mechanical & Aerospace Engineering Theses & Dissertations
Behavior of an axisymmetric equilibrium turbulent boundary layer disturbed by a propeller wake in the freestream was investigated experimentally. Tests were conducted in a low speed wind tunnel and measurements of turbulence quantities were made using an X wire probe and a constant temperature anemometer. The boundary layer flow on a cylindrical body was characterized by measuring its gross parameters and comparing them with classical values. Propeller speed was measured using an electronic circuit whose output signal was also used to trigger hot wire probe. Gross boundary later characteristics of the disturbed boundary layer did not deviate appreciably from the …
Investigation Of Vscous/Inviscid Interaction In Transonic Flow Over Airfoils With Suction, Chadra S. Vemuru
Investigation Of Vscous/Inviscid Interaction In Transonic Flow Over Airfoils With Suction, Chadra S. Vemuru
Mechanical & Aerospace Engineering Theses & Dissertations
The viscous/inviscid interaction over transonic airfoils with and without suction is studied. The streamline angle at the edge of the boundary layer is used to couple the viscous and inviscid flows. The potential flow equations are solved for the inviscid flow field. In the shock region the Euler equations are solved using the method of integral relations. For this the potential flow solution is used as the initial and boundary conditions. An integral method is used to solve the laminar boundary-layer equations. Since both methods are integral methods, a continuous interaction is allowed between the outer inviscid flow region and …
A Similarity Model For Flow In A Turbulent Boundary Layer, Earl Clark Lemmon
A Similarity Model For Flow In A Turbulent Boundary Layer, Earl Clark Lemmon
Theses and Dissertations
One of the basic goals in engineering is to generate models which will provide a means for analytically predicting observed phenomenon. Such a model is often modified several times to obtain better results. The purpose of this study was to generate a model for an equilibrium turbulent boundary layer for steady flow over a flat plate and compare the results obtained by using the model with experimental data. Part of the objective was to also suggest ways in which the model could be modified to obtain better results.
The Development Of Turbulent Flow In The Inlet Region Of Smooth Pipe, Forrest C. Smith
The Development Of Turbulent Flow In The Inlet Region Of Smooth Pipe, Forrest C. Smith
Theses and Dissertations
Turbulent flows are encountered in nearly every case where fluid motion is involved. Turbulent flow in pipes is of great practical interest, and the problem of flow in the entry region is of special importance since the great majority of applications are in the realm of developing flow.
Turbulent Flow In The Entry Region, Chin-Hsiu Li
Turbulent Flow In The Entry Region, Chin-Hsiu Li
Theses and Dissertations
When entering into the subject of turbulent flow, it is essential to understand that the kind of flow with which we deal belongs to a particular class known as shear flow. These types of flow comprise flow fields in which relative velocities have been induced by shear stresses rather than by the action of pressure forces. In pipe flow, when the fluid enters through the well-rounded bell from a reservoir or from the calm open air, a uniform velocity distribution occurs at the pipe entrance. Immediately down stream from the entrance of the pipe, the flow is structured with a …
Heat Transfer In Shock Boundary Layer Interaction Regions, Rex W. Shumway
Heat Transfer In Shock Boundary Layer Interaction Regions, Rex W. Shumway
Theses and Dissertations
The interest in aerodynamic heating problems has been increasing rapidly in the last decade. This interest is no longer concentrated on the heating of simple shapes for which adequate heat transfer theory has been developed« Because of the increasing Mach number ranges of aircraft, the need for information on the aerodynamic heating of various components has become imperative. Only when the magnitude of the problem has been exposed can the design for reducing the severity of local heating be optimized. Definition of these problems is of interest, not only because of the flow phenomena, but because of possible design limitations …