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Laser velocimetry applied to transonic and supersonic aerodynamicsAs a further demonstration of the capabilities of laser velocity in compressible aerodynamics, measurements obtained in a Mach 2.9 separated turbulent boundary layer and in the transonic flow past a two-dimensional airfoil section are presented and compared to data realized by conventional techniques. In the separated-flow study, the comparisons were made against pitot-static pressure data. Agreement in mean velocities was realized where the pressure measurements could be considered reliable; however, in regions of instantaneous reverse velocities, the laser results were found to be consistent with the physics of the flow whereas the pressure data were not. The laser data obtained in regions of extremely high turbulence suggest that velocity biasing does not occur if the particle occurrence rate is low relative to the turbulent fluctuation rate. Streamwise turbulence intensities are also presented. In the transonic airfoil study, velocity measurements obtained immediately outside the upper surface boundary layer of a 6-inch chord MACA 64A010 airfoil are compared to edge velocities inferred from surface pressure measurements. For free-stream Mach numbers of 0.6 and 0.8, the agreement in results was very good. Dual scatter optical arrangements in conjunction with a single particle, counter-type signal processor were employed in these investigations. Half-micron-diameter polystyrene spheres and naturally occurring condensed oil vapor acted as light scatterers in the two respective flows. Bragg-cell frequency shifting was utilized in the separated flow study.
Document ID
19770004281
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Johnson, D. A.
(NASA Ames Research Center Moffett Field, CA, United States)
Bachalo, W. D.
(NASA Ames Research Center Moffett Field, CA, United States)
Moddaress, D.
(NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
August 8, 2013
Publication Date
May 1, 1976
Publication Information
Publication: AGARD Appl. of Non-Intrusive Instr. in Fluid Flow Res.
Subject Category
Aerodynamics
Accession Number
77N11224
Distribution Limits
Public
Copyright
Other
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