On the oblique breakdown mechanism in a supersonic boundary layer on a swept wing at Mach 2

Abstract

Abstract.The results of an experimental study of the controlled pulsations development in the spanwise modulated boundary layer of a swept wing are presented in the paper. The experiments were conducted at Mach 2 and unit Reynolds number Re1 = 6×10 6 m -1 . The square stickers were applied to induce the spanwise modulation of mean flow in the boundary layer. It was obtained, that the presence of roughness leads to a decrease of the disturbance source efficiency at the subharmonic and fundamental frequency, and the oblique breakdown mechanism begins to appear at smaller values of the longitudinal coordinate x as compared with the case of a smooth wing.

Mechanism for frustum transition over blunt cones at hypersonic speeds

“…For the nonlinear computations, the five components (ρ,ũ,ṽ,w,T) of the linear non-modal disturbance field from figure 4 are extracted at the inflow location of ξ = 0.03 m. Specifically, an inflow disturbance composed of a pair of oblique travelling waves with f = 250 kHz and m = ±50 is used to investigate the possibility of oblique-mode breakdown. The salient features of oblique-mode breakdown involving linearly unstable modes have been reported both for incompressible boundary layers (where the nonlinear interaction between a pair of oblique Tollmien-Schlichting waves (Berlin, Lundbladh & Henningson 1994) drives the breakdown process) and for supersonic boundary layers (that involve the interaction between a pair of oblique first-mode waves (Thumm 1991;Joslin, Streett & Chang 1992;Adams & Kleiser 1993;Fasel, Thumm & Bestek 1993;Chang & Malik 1994;Laible, Mayer & Fasel 2009;Mayer, Von Terzi & Fasel 2011;Laible & Fasel 2016;Panina et al 2017) and between a pair of oblique Mack-mode waves (Sivasubramanian & Fasel 2013)). The present oblique-mode breakdown differs from the aforementioned cases because it is initiated by the interaction between a pair of oblique travelling waves that peak within the entropy layer beyond the boundary-layer edge.…”