Accession Number : ADA308574

Title :   A Physical and Numerical Study of Three-Dimensional Skewed Mixing Layers.

Descriptive Note : Final rept. 15 Aug 91-14 Nov 95,

Corporate Author : STANFORD UNIV CA DEPT OF AERONAUTICS AND ASTRONAUTICS

Personal Author(s) : Lee, Sanjiva K.

PDF Url : ADA308574

Report Date : 14 JAN 1996

Pagination or Media Count : 23

Abstract : The effect of skewing the two freestreams on the development of a compressible mixing layer was studied. The results of stability analysis show that skewing has the simultaneous effect of increasing the effective velocity ratio, which is a destabilizing effect, and increasing the effective, convective Mach number, which is a stabilizing effect. Direct numerical simulations of a spatially evolving mixing layer with equal velocity magnitude but skewed in opposite directions were conducted to study the non-linear evolution. Three skewing angles were considered: 30, 60, and 90 deg. For the low skewing angle cases, the mixing layer rolls up and forms a pattern of streamwise vortices. For the 90 deg case, vortex breakdown was observed, which significantly enhances the mixing. For high Mach numbers, oblique waves are more unstable which form a pattern of streamwise vortices with increasing spanwise undulation. The skewing effect can be practically realized by adding swirl to a circular mixing layer. Results of stability analysis show that adding a small amount of swirl near the center of the mixing layer significantly enhances the maximum amplification rate, and the enhancement sustains under compressible conditions. The disturbance energy budget shows that a significant of disturbance energy is extracted from the shear in the swirl component.

Descriptors :   *JET MIXING FLOW, STABILIZATION, ANGLES, RATIOS, STABILITY, LAYERS, NUMERICAL ANALYSIS, VORTICES, COMPRESSIBLE FLOW, NONLINEAR SYSTEMS, WIND SHEAR, PATTERNS, MACH NUMBER.

Subject Categories : Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE