Quantitative visualization of compressible turbulent shear flows using condensate-enhanced Rayleigh scattering

This paper describes several flow visualization experiments carried out in Mach 3 and Mach 8 turbulent shear flows. The experimental technique was based on laser scattering from particles of H2O or CO2 condensate that form in the wind tunnel nozzle expansion process. The condensate particles vaporiz...

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Bibliographic Details
Published in:Experiments in fluids 2004-09, Vol.37 (3), p.438-454
Main Authors: POGGIE, J, ERBLAND, P. J, SMITS, A. J, MILES, R. B
Format: Article
Language:English
Subjects:
Boundary layer and shear turbulence
Compressible flows
shock and detonation phenomena
Condensates
Exact sciences and technology
Fluid dynamics
Fluid flow
Fluids
Fundamental areas of phenomenology (including applications)
Instrumentation for fluid dynamics
Physics
Shear flow
Shear layers
Supersonic and hypersonic flows
Turbulence
Turbulent flow
Turbulent flows, convection, and heat transfer
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Summary:This paper describes several flow visualization experiments carried out in Mach 3 and Mach 8 turbulent shear flows. The experimental technique was based on laser scattering from particles of H2O or CO2 condensate that form in the wind tunnel nozzle expansion process. The condensate particles vaporize extremely rapidly on entering the relatively hot fluid within a turbulent structure, so that a sharp vaporization interface marks the outer edge of the rotational shear layer fluid. Calculations indicate that the observed thin interface corresponds to a particle size of 10 nm or less, which is consistent with optical measurements, and that particles of this size track the fluid motions well. Further, calculations and experiments show that the freestream concentration of condensate required for flow visualization has only a small effect on the wind tunnel pressure distribution. Statistics based on the image data were compared to corresponding results from probe measurements and agreement was obtained in statistical measures of speed, scale, and orientation of the large-scale structures in the shear layer turbulence. The condensate-enhanced Rayleigh scattering technique is judged to be a useful tool for quantitative studies of shear layer structure, particularly for identifying the instantaneous boundary layer edge and for extracting comparative information on the large-scale structures represented there.
ISSN:0723-4864
1432-1114
DOI:10.1007/s00348-004-0828-9