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

Report Date:

1996-04-01

Pagination or Media Count:

129.0

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.

Subject Categories:

  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE