Spatial and temporal alterations due to vortex generators in a flare induced shock–boundary layer interaction

Abstract

This paper describes the modifications instigated in a flare induced shock–boundary layer interaction flowfield by two vortex generators viz. Baseline Ramps (BRs) and Ramped Vanes (RVs). Experimental and computational investigations were conducted at Mach 2, on a cone–cylinder–flare model, with a flow turning angle of 24° at the cylinder–flare juncture. The vortex generators were placed 50 mm (10δ) upstream of the compression corner and their height was 50% of the local boundary layer thickness (h = 2.1 mm = 0.5δV G). The counter-rotating vortices emanated by Baseline Ramps (BRs), remained in close proximity to one another and interacted strongly along the upwash regions. Hence, they quickly dissipated and moved away from the model surface, causing only a nominal impact on the interaction region. Alternatively, the vortices produced by Ramped Vanes (RVs) were amply separated and therefore, largely retained their core strength and were not rapidly advected away from the near-wall region. As a result, the separation occurred a little prematurely in the upwash regions and was significantly delayed along the downwash regions. Additionally, tornado-like vortices were formed, due to the streamwise vortices interacting with the separation bubble. The delay in separation along the downwash regions, also brought the separation shock closer to the compression corner. This was accompanied by a suitable increase in the shock’s oscillating frequency, in such a way that the Strouhal number based on the interaction length (distance between the corner and the mean position of the separation shock foot) remained more or less the same.