Excitation of cross-flow instability modes of a swept-wing boundary layer due to vibrational and vortex-vibration localized receptivity mechanisms

Abstract

Results of the EU project RECEPT are presented. The experiments in a three-dimensional swept-wing boundary layer were carried out in the low-turbulence wind tunnel MTL at KTH Stockholm. The cross-flow instability modes (CF) were the most amplified ones, while the Tollmien-Schlichting instability modes were suppressed by a favorable pressure gradient. The main measurements were performed by means of a single-wire hot-wire probe at conditions of excitation of fully controlled, unsteady surface and flow perturbations. These perturbations were excited by special sources: (i) a surface membrane and (ii) a vibrating wire. Comparisons with calculations carried out by means of linear (locally-parallel) stability theory (LST) were performed. A thorough analysis of the disturbance development showed that the features of the downstream evolution of the CF-modes observed at the combinational frequency can be explained by the action of a distributed receptivity mechanism.