An investigation of interactions between normal shocks and transitional boundary layers

Abstract

The effect of transition location on the interaction between normal shock waves and boundary layers is an area of study that has been enjoying a resurgence in interest recently, as operating regimes change and it becomes a phenomenon that may occur in flight. The problem is critical because a laminar boundary layer will typically separate at even a weak shock, with detrimental impact on the flow, when a turbulent boundary layer might remain attached. However, ahead of the shock the laminar boundary layer often preferable due to its lower drag. This investigation aims to explore the interaction between normal shocks and laminar/transitional flat plate boundary layers to gain insights into the fundamental flow physics of the problem. The flow is difficult to investigate experimentally, as although flat plate transition has been studied for many years, achieving the same phenomenon at high speeds and moderate Reynolds numbers is more challenging due to higher tunnel noise levels in comparison with flight or lower Reynolds number 'quiet tunnels'. This paper documents how an experiment has been developed with a laminar flat plate boundary layer and an incident normal shock wave. Transition has been triggered upstream of the shock, and some initial results of these transitional interactions are presented. © Todd Davidson and Holger Babinsky.