Accession Number : ADA310025

Title :   The Effects of Expansion Regions on the Turbulence Structure of a Supersonic Boundary Layer.

Descriptive Note : Final rept. 1 Jan 94-31 Mar 96,

Corporate Author : OHIO STATE UNIV COLUMBUS DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Samimy, M. ; Arnette, S. A. ; Elliott, G. S.

PDF Url : ADA310025

Report Date : APR 1996

Pagination or Media Count : 129

Abstract : A fully-developed high Reynolds number Mach 3 turbulent boundary layer and the effects of four expansion regions (centered and gradual expansions of 7 deg and 14 deg) on the boundary layer were investigated by utilizing 1) multi-point instantaneous surface pressure measurements, 2) instantaneous single- and double-pulse flow visualizations based on Filtered Rayleigh Scattering (FRS), 3) two-component planar velocity measurements using Filtered Planar Velocimetry (FPV), and 4) detailed turbulence measurements using Laser Doppler Velocimetry (LDV). Flow visualization results indicate that the upper half of the fully developed turbulent boundary layer is populated with elongated longitudinal structures of considerable streamwise but very limited spanwise extent. These structures are randomly distributed in space and time and survive even the 14 deg centered expansion. The visualizations also show that large scale structures increase both in size and angle and small scale structures are quenched across the expansions. The angle of large scale structures return to the flat plate value further downstream of the expansions. The normalized power spectra of pressure fluctuations downstream of the expansions are more concentrated at lower frequencies than their upstream counterparts, confirming the small scale quenching shown by flow visualizations.

Descriptors :   *TURBULENT BOUNDARY LAYER, *SUPERSONIC FLOW, PRESSURE GRADIENTS, LASER INDUCED FLUORESCENCE, TURBULENCE, TURBULENT FLOW, POWER SPECTRA, COMPUTATIONAL FLUID DYNAMICS, FLOW VISUALIZATION, PRESSURE MEASUREMENT, COMPRESSIBLE FLOW, FLOW FIELDS, RAYLEIGH SCATTERING, SHEAR STRESSES, KINETIC ENERGY, NONEQUILIBRIUM FLOW, MACH NUMBER, FREE STREAM, STATIC PRESSURE, PRESSURE DISTRIBUTION, REYNOLDS NUMBER, BOUNDARY LAYER CONTROL, SHEAR FLOW, BOUNDARY LAYER FLOW, LASER VELOCIMETERS, FLAT PLATE MODELS, VARIABLE PRESSURE.

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE