Unsteadiness in Shock Wave Boundary Layer Interactions across Multiple Interaction Configurations

Abstract

The effects of interaction strength and configuration generality are the subject of an experimental investigation to assess the low frequency unsteadiness typically observed in Shock Wave Boundary Layer Interactions (SWBLIs). The core dominant mechanisms responsible remain disputed due to the lack of a broad approach for understanding what drives each mechanism across a range of interaction types. This paper forms the first part of an investigation to observe various interactions in a well characterized baseline environment. Experiments have been conducted in the Imperial College London supersonic wind tunnel where three configurations of SWBLI have been tested, each with a strength of interaction designed to result in incipient separation: a) 14 • compression ramp interaction (Mach 2.0), b) 8 • incident shock reflection interaction (Mach 2.0), and c) normal shock interaction (Mach 1.4). Analysis has been conducted using high-speed planar two-component particle image velocimetry and schlieren photography to characterize the baseline flow and inspect shock unsteadiness. Each configuration exhibits similar levels of incipient separation with probabilities of reversed flow between 12% and 26% in each frame. Significant energy content has been observed within the interactions at frequencies far lower than typically witnessed in a supersonic boundary layer, providing agreement with results in literature.

Unsteady Flow Features Across Different Shock/Boundary-Layer Interaction Configurations

“…This data was fitted to an estimation of particle response to a step change in velocity, modeled by an exponential decay with additional spatial smoothing due to the finite PIV interrogation window size. 39 The characteristic particle response was fitted for each trace.…”

“…Schlieren photographs for typical interactions for each type of configuration (images taken in present facility39 ).…”

“…Composite flow visualizations of typical interactions for each type of configuration using surface oil-flow visualization and planes of velocity fluctuation fields extracted from PIV results (images taken in present facility39 ). a manual lead screw mechanism the ramp can be positioned continuously along a travel of 76 mm, spanning the test locations.…”