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Aerodynamics and Fluid Mechanics Commons™

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1993

Articles 1 - 14 of 14

Full-Text Articles in Aerodynamics and Fluid Mechanics

Evaluation Of A Concentration Probe For Application In A Supersonic Flow Field, John S. Alsup Dec 1993

Evaluation Of A Concentration Probe For Application In A Supersonic Flow Field, John S. Alsup

Theses and Dissertations

Aspirating, concentration probes are used to measure binary gas concentrations in a supersonic flow. In the past, a tank discharge method has been used to calibrate concentration probes. An alternate calibration method has been developed and tested on a probe in a steady, subsonic/sonic flow. This study evaluated the calibration and performance of a concentration probe in a steady, supersonic flow over a range of mixture ratios of air and helium. The results of this study and a comparison of the two calibration methods are presented.

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Off-Design Performance Of Crenulated Blades In A Linear Compressor Cascade, Michael J. Costello Dec 1993

Off-Design Performance Of Crenulated Blades In A Linear Compressor Cascade, Michael J. Costello

Theses and Dissertations

The effects of using compressor blades with a crenulated (notched) trailing edge in a low aspect ratio (AR= 1) linear compressor cascade at four incidence angles (-1.08°, +4.49°, +9.32° and +12.44°) were investigated. Blade performance and wake mixing characteristics for crenulated blades were compared with similar data for blades with a straight trailing edge. A seven-bladed cascade was operated with a flow Mach number of 0.4 and a blade chord Reynolds number of 4.1 (10)5. The diffusion factor ranged from 0.22 to 0. 42 and strong three-dimensional flow effects were present. Total pressure losses were measured with a …

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Effects Of Crenulations On Three Dimensional Losses In A Linear Compressor Cascade, William L. Spacy Ii Dec 1993

Effects Of Crenulations On Three Dimensional Losses In A Linear Compressor Cascade, William L. Spacy Ii

Theses and Dissertations

An experimental investigation into the effect of compressor blade trailing edge geometry on three-dimensional flows in a linear cascade was conducted at the AFIT linear cascade test facility. Hot-wire/hot-film anemometry along with total pressure instrumentation was used to analyze crenulation generated vortices and their interaction with the three-dimensional flows in the cascade. The effects of this interaction on the performance parameters associated with the cascade were quantified. The results-indicate that wake mixing is better for crenulated trailing edges and that the precise geometry of the crenulations is critical to performance. One crenulation geometry was found to increase wake mixing while …

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Analysis Of The Effects Of Wake Passage On Heat Transfer In A Linear Turbine Cascade, Kevin S. Allen Dec 1993

Analysis Of The Effects Of Wake Passage On Heat Transfer In A Linear Turbine Cascade, Kevin S. Allen

Theses and Dissertations

This study investigated the effect of wake passage on the heat transfer in a linear turbine cascade. The apparatus used was the Air-Force Institute of Technology linear Turbine Cascade Test Facility (TCTF). The TCTF was fitted with a be Pulley system to facilitate a series of translating bars. The bars, when passed d upstream of the cascade, created a series of wakes. The parameters varied were freestream model Reynolds number and bar conditions, i.e. , bars in, bars out, and bar passing frequency. One blade in the TCTF was instrumented to allow pressure and temperature measurements at discrete points on …

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A Numerical Study Of High-Speed Missile Configurations Using A Block- Structured Parallel Algorithm, Douglas C. Blake Dec 1993

A Numerical Study Of High-Speed Missile Configurations Using A Block- Structured Parallel Algorithm, Douglas C. Blake

Theses and Dissertations

A numerical analysis of the aerodynamic phenomena associated with the high-speed flight of a sharp-nosed, four-finned, high-fineness ratio missile using a block-structured, parallel computer algorithm is presented. The algorithm, PANS-3EM, utilizes a second-order-accurate, shock-capturing, Total Variation Diminishing scheme and incorporates a Baldwin-Lomax turbulence model. PANS-3EM allows for extreme flexibility in the choice of computational domain decomposition and computing machine of implementation. Developmental work consists of conceptualization and verification of the algorithm as well as parallel performance and scalability studies conducted on a variety of computing platforms. Using PANS-3EM, the aerodynamic characteristics of the missile are investigated. Drag and pitching moment …

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Wake Passage Effects On The Losses In A Linear Turbine Cascade, James A. Braunschneider Dec 1993

Wake Passage Effects On The Losses In A Linear Turbine Cascade, James A. Braunschneider

Theses and Dissertations

A linear turbine cascade was used to investigate the effects of wake passage due to stator-rotor interaction. The wakes were modeled by passing 1.98 mm (0.078 in) diameter bars upstream of a linear cascade blade row. Total pressure loss coefficients, mass averaged total pressure loss coefficients and velocities were used to characterize the effects of wake passage. Bar passing frequencies of 80, 160, 320 bars/sec were tested. These frequencies were tested, with the bars at 6.35 mm (0.25 in) intervals and at two Reynolds numbers, 341, 000 and 45,5000 Bar spacings of 12.7 mm (0.5 in), and 89 mm (3.5 …

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Rendering Of Three-Dimensional Data Sets Derived From Finite-Difference And Spectral Methods, Paul A. Schubert Dec 1993

Rendering Of Three-Dimensional Data Sets Derived From Finite-Difference And Spectral Methods, Paul A. Schubert

Theses and Dissertations

The timely visualization of three-dimensional data sets and the advantages of using a spectral method solution versus a finite-difference method solution in rendering isosurfaces is described. The Beam-Warming numerical algorithm, which uses implicit-approximate-factorization, is used to generate the steady-state solutions for a model diffusion-convection problem. The Chebyshev collocation operator is used to evaluate the right-hand side of the Beam-Warming algorithm for the spectral solution. Comparing the model problem results with the exact solution, the spectral series solution is truncated to the same degree of accuracy as the finite-difference for comparison of rendering times. The rendering algorithm employs octrees to efficiently …

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A Numerical Determination Of Bifurcation Points For Low Reynolds Number Conical Flows, Larry K. Waters Dec 1993

A Numerical Determination Of Bifurcation Points For Low Reynolds Number Conical Flows, Larry K. Waters

Theses and Dissertations

It has long been established that supersonic flow over axisymmetric conical bodies at high angles of attack tend to develop a side force due to vortical asymmetry. One of the proposed reasons for the asymmetry is a bifurcation point in the solution of the Navier-Stokes equations. This study investigated the possible existence of a bifurcation point in the Navier-Stokes equations for subsonic flow. Newton's method, with gauss elimination, was used- to solve the steady-state, viscous, compressible Navier-Stokes equations in spherical coordinates assuming conical similarity.

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Simulation Of Vertical Tail Buffet In Internal Vortex Breakdown Flows, Mark William Flanagan Oct 1993

Simulation Of Vertical Tail Buffet In Internal Vortex Breakdown Flows, Mark William Flanagan

Mechanical & Aerospace Engineering Theses & Dissertations

Computational simulation of vertical tail buffet in an internal vortex breakdown flow is considered. The fiuid-flow problem is formulated using the full, compressible, unsteady Navier-Stokes equations which are solved using an implicit, flux-difference splitting, finite volume scheme. The fluid-flow problem is solved in a configured circular duct using quasi-axisymmetric assumptions to simplify the flow equations. A plate is placed transverse to the incoming flow. Solution of the flow in the duct is performed with and without a rigid plate, and with and without an elastic plate. The elastic response of the plate is calculated assuming that it is a cantilever …

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Computation Of The Aerodynamic Characteristics Of A Subsonic Transport Aircraft Using A Panel Method, Lillianne Plaster Whitelock Troeger Oct 1993

Computation Of The Aerodynamic Characteristics Of A Subsonic Transport Aircraft Using A Panel Method, Lillianne Plaster Whitelock Troeger

Mechanical & Aerospace Engineering Theses & Dissertations

An advanced low-order panel method, VSAERO, is applied to a full-configuration transport aircraft. Wing pressure distributions as well as lift, drag, and pitching moment coefficients calculated for the full computational configuration are compared with experimental data. In addition, partial configurations are evaluated computationally to determine the relevance of certain complex aircraft components to the computations. It is shown that the wing-surface pressure distributions and pitching moment coefficient are well predicted by VSAERO. The lift coefficient is consistently overpredicted by the code.

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Simultaneous Aerodynamic Analysis And Design Optimization, Satish Venkatasubra Mani Oct 1993

Simultaneous Aerodynamic Analysis And Design Optimization, Satish Venkatasubra Mani

Mechanical & Aerospace Engineering Theses & Dissertations

An efficient approach for simultaneous aerodynamic analysis and design optimization is presented. Using this approach, the expensive procedure of performing complete steady— state flow analyses at every design-optimization step is avoided, thus addressing the challenge of incorporating computational fluid dynamics software into efficient gradient—based optimization techniques for aerodynamic design. An adjoint—variable method is introduced to nullify the effect of an increased number of design variables in this problem formulation. This approach is successfully tested on two quasi—one—dimensional nozzle—flow problems: a fully supersonic flow, and also a transonic flow with a normal shock. The algorithm is implemented using the direct Newton—iteration …

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A Comparison Of Computational And Experimental Data For A Subscale High Speed Propulsive Nozzle At Low Mach Numbers, Yonghee Hyun Jun 1993

A Comparison Of Computational And Experimental Data For A Subscale High Speed Propulsive Nozzle At Low Mach Numbers, Yonghee Hyun

Theses and Dissertations

This computational study of a hypersonic sub-scale nozzle/cowl configuration compares numerical solutions with experimental data for nozzle performance at off design conditions (subsonic through supersonic Mach numbers. A combination of Van Leer and Roe flux-splitting algorithms was used to solve the flow field. The explicit formulation assumed laminar planar flow and the perfect gas equation of state. A validation for the numerical algorithm was accomplished by comparing with experimental data for a variety of cases. Grid refinement, geometry, and operating conditions all influenced the comparison of the experimental and computational data. Generally, as the Mach number and nozzle pressure ratio …

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Hoph Bifurcation In Viscous, Low Speed Flows About An Airfoil With Structural Coupling, Mark J. Lutton Mar 1993

Hoph Bifurcation In Viscous, Low Speed Flows About An Airfoil With Structural Coupling, Mark J. Lutton

Theses and Dissertations

The locations of Hopf bifurcation points associated with the viscous, incompressible flow about a NACA 0012 airfoil with structural coupling are computed for very low Reynolds numbers (<2000). A semi-implicit, first-order-accurate time integration algorithm is employed to solve the stream function-vorticity form of the Navier-Stokes equations. The formulation models the inclusion of simple structural elements affixed to the airfoil and captures the resulting airfoil motion. The equations describing the airfoil motion are integrated in time using a fourth-order Runge-Kutta algorithm. The dissertation is divided into two parts. In part one, numerical experiments are performed in the laminar regime to determine if the structural model of the airfoil has an effect upon the location of the Hopf bifurcation point when compared with the fixed airfoil. Results are reported for a variety of structural characteristics, including variations of torsional and linear spring constants, inertial properties, structural coupling, and structural damping. The structure of the solution space is explored by means of phase plots. In part two, the Baldwin-Lomax turbulence model is implemented to model turbulent flow. A numerical effort is made to predict the onset of unsteady flow.

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Simplified Jet-A Kinetic Mechanism For Combustor Application, Bahman Ghorashi, Chi-Ming Lee, Krishna Kundu Jan 1993

Simplified Jet-A Kinetic Mechanism For Combustor Application, Bahman Ghorashi, Chi-Ming Lee, Krishna Kundu

Scholarship Collection

Successful modeling of combustion and emissions in gas turbine engine combustors requires an adequate description of the reaction mechanism. For hydrocarbon oxidation, detailed mechanisms are only available for the simplest types of hydrocarbons such as methane, ethane, acetylene, and propane. These detailed mechanisms contain a large number of chemical species participating simultaneously in many elementary kinetic steps. Current computational fluid dynamic (CFD) models must include fuel vaporization, fuel-air mixing, chemical reactions, and complicated boundary geometries. To simulate these conditions a very sophisticated computer model is required, which requires large computer memory capacity and long run times. Therefore, gas turbine combustion …

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