Accession Number:

ADA280579

Title:

Effect of Pressure Gradient on First Mode of Instability in High-Speed Boundary Layers

Descriptive Note:

Contractor rept.

Corporate Author:

INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA

Personal Author(s):

Report Date:

1994-04-01

Pagination or Media Count:

51.0

Abstract:

The effect of a pressure gradient on the first mode of instability of compressible subsonic and supersonic boundary layers is investigated using linear stability theory. Formulations are presented for nonsimilar boundary- layer mean flow and linear quasi-parallel stability problems that account for variable fluid properties. A pressure gradient is studied that generates potential-flow Mach number distributions at the edge of the boundary layer of the form M, cxn, where c is a constant and x is the dimensionless streamwise distance. Variations are calculated for the maximum growth rates of three- dimensional first-mode waves with different edge Mach numbers and different levels of both adverse and favorable pressure gradients. A favorable pressure gradient is shown to have a stabilizing effect on first-mode waves. However, at high edge Mach numbers, a favorable pressure gradient becomes less effective in stabilizing first-mode waves. The frequencies and streamwise and spanwise wave numbers that correspond to the maximum growth rates of first-mode waves decrease as the pressure gradient become more favorable at all Mach numbers when the Reynolds number R 1500 and at Me2 when R 600. Setting the Prandtl number to unity significantly increases the maximum growth rates of first- and second-mode waves at high Mach numbers compared with setting it to the realistic value of 0. 72. Pressure gradient, stability, supersonic, boundary layers

Subject Categories:

  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE