Accession Number:

ADA222297

Title:

Inviscid Dynamics of Unstable Shear Layers

Descriptive Note:

Technical rept. 1 Aug 1987-1 Aug 1988

Corporate Author:

R AND D ASSOCIATES MARINA DEL REY CA

Report Date:

1990-04-01

Pagination or Media Count:

78.0

Abstract:

Numerical simulations are described for three idealized shear layer problems typical of shock reflection flow fields free shear layers corresponding to a slip line emanating from a triple point, a wall shear layer approximating a boundary layer behind a shock, and a wall jet similar to those found in precursor and double-Mach-stem flows. The dynamic evolution of the shear layers was followed by means of numerical solutions of the inviscid conservation laws of gasdynamics. The inviscid shear layer discontinuity was de- singularized by initializing the flowfield with a Tanhy velocity profile that, in effect, allows one to resolve the shear layer on the computational mesh. The inflow velocity profile was then perturbed with the fundamental frequency from linear stability analysis and its subharmonics. The macroscopic features of the calculations e.g., the formation and growth of large-scale rotational structures, the visual spreading rates, and the mean flow profiles agree quantitatively with the available experimental data. The fluctuating flow components agree qualitatively e.g., the peak velocity fluctuations can be 1.5 to 2 times larger than the data, because of the two-dimensional flow approximation. These calculations demonstrate that the fluctuating, time- dependent flow variations observed in such problems are caused by the dynamic evolution of unstable shear layers, and that the dynamics is dominated by inviscid effects for such large-Reynolds-number flows.

Subject Categories:

  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE