A Study of Compressible Turbulent Free Shear Layers Using Laser Doppler Velocimetry (Supersonic Flow, Mixing, Recirculating)
Petrie, Howard Lane
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https://hdl.handle.net/2142/70121
Description
Title
A Study of Compressible Turbulent Free Shear Layers Using Laser Doppler Velocimetry (Supersonic Flow, Mixing, Recirculating)
Author(s)
Petrie, Howard Lane
Issue Date
1984
Department of Study
Mechanical Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Abstract
An experimental investigation of compressible, two-dimensional planar, turbulent free shear layers formed by the separation of a Mach 2.43 flow over a backward facing step was conducted. Two different wind tunnel test sections were used to achieve a constant pressure separation of the shear layer at the backstep corner so that the developing free shear layer was unaffected by separation effects. Sidewall static pressure measurements, Schlieren photographs, surface oil flow visualization, and two channel coincident laser Doppler velocimeter measurements were made. Streamwise component turbulence intensities were found to be comparable to incompressible mixing layer results which contrasts with the limited existing hot-wire anemometer data. Transverse velocity component turbulence intensities, turbulence shear stresses, shear layer growth rates, and shear layer entrainment rates were all significantly smaller than incompressible mixing layer values. The maximum turbulent shear stresses determined by the coincident two channel LDV measurements were in agreement with the results and trends of others. Free shear layer turbulent stresses and mass flow entrainment rates were increased as a result of flow recirculation. The recirculating flow was directed towards the backstep separation point and this may relate to the onset of plume induced separation on missile afterbodies. LDV statistical velocity bias was experimentally confirmed and a two-dimensional velocity inverse weighting factor was found to correct for the bias reasonably well. The problem of LDV fringe bias for two-channel coincident LDV systems in highly turbulent high speed flows was examined in detail analytically.
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