DNS of Boundary-Layer Receptivity to Freestream Sound for Hypersonic Flows Over Blunt Elliptical Cones

Abstract

This paper is concerned with the problem of leading-edge receptivity of 3-D hypersonic boundary layers over a blunt elliptical cone. The receptivity of boundary layers to disturbances is the process of converting environmental disturbances into instability waves in the boundary layers. It provides important initial conditions in terms of amplitude, frequency, and phase for the study of development of instability waves in the boundary layers (Goldstein, 1989; Saric, 1994). Most theoretical results on boundary-layer receptivity have been obtained from the asymptotic analysis of incompressible flows. The asymptotic analysis explains how the long wavelength freestream acoustic disturbances enter a boundary layer and generate short-wavelength Tollmien-Schlichting (T-S) waves downstream of the leading edge. Recently, direct numerical simulation (DNS) of the Navier-Stokes equations has been used as a research tool in the studies of stability and transition. Examples of the DNS studies on the receptivity of boundary layers can be found in (Murdock, 1981; Lin, 1992; Buter, 1994: Casalis, 1994; Corke, 1996). Most of these studies have been for incompressible or low-speed compressible boundary layers.