Critical decoupling criterion for dual-incident shock wave/turbulent boundary layer interaction

Abstract

Interaction zones resulting from the dual-incident shock wave/turbulent boundary layer interactions (D-ISWTBLI) typically exhibit one of two distinct flow patterns: the formation of two isolated small-scale interaction zones following decoupling or the presence of a coupled large-scale interaction zone. This paper investigates the underlying mechanism governing the transition of the flow field of D-ISWTBLI, shifting from a coupled flow pattern to an isolated one. To achieve this, we employ numerical simulations and propose a criterion for determining the critical decoupling condition. Our study commences by presenting an analysis of the time-averaged pressure distribution along-the-wall and the corresponding changes in the characteristic scale of the coupled interaction zone as the spacing between the shock incident points continuously increases. We elucidate the variation mechanism of the characteristic scale by analyzing the flow field. Subsequently, based on the intrinsic relationships among the characteristic scales of the coupled interaction zone in their critical state, we establish a relational expression that links the critical decoupling spacing with the characteristic scales of the interaction zone in the critical state. We then employ numerical simulation data, accounting for key influencing factors such as the intensity ratio of the individual incident shock components comprising the dual-incident shock system, the overall intensity of the dual-incident shock system, and the free-stream conditions to determine the critical decoupling condition. This critical decoupling condition effectively delineates the flow pattern of the interaction zone under various free-stream conditions and shock configurations, a conclusion that is corroborated by published experimental data.