Investigation of shock-induced boundary-layer transition in transonic high Reynolds number flows using Temperature-Sensitive Paints

Abstract

Shock-wave / boundary-layer interaction (SWBLI) is a complex phenomenon occurring in a variety of flows. On laminar and supercritical wings at transonic flow conditions and chord Reynolds numbers up to approximately 20 million, SWBLI can be involved in the transition process leading the laminar boundary layer to turbulence. At small angles of attack (typically below 1.5°), the laminar boundary layer over the suction side of the wing is accelerated, and therefore stabilized, for a significant portion of the wing chord length. The supersonic flow region is then terminated by a shock that interacts with the boundary layer; in particular, the abrupt pressure increase induces the formation of a laminar separation bubble, and the foot of the shock has a characteristic λ-structure. Transition occurs within the laminar separation bubble and is investigated in the present work by means of the Temperature-Sensitive Paint (TSP) measurement technique. Results of SWBLI in transitional boundary layers, obtained on natural laminar flow and supercritical airfoil models at transonic flow conditions and high Reynolds numbers, will be presented and analyzed in this contribution.