Study of Unsteadiness due to 3-D Shock-Boundary Layer Interaction in Flow over a Square-faced Protuberance

TL;DR

This study investigates the unsteady flow dynamics caused by 3-D shock-boundary layer interactions over a square-faced protuberance using wind tunnel experiments, schlieren imaging, pressure measurements, and advanced data analysis techniques.

Contribution

It introduces a comprehensive experimental analysis of 3-D shock-induced unsteadiness, employing DMD and correlation analysis to characterize flow physics and shock motion coherence.

Findings

Mean shock foot oscillates with a Strouhal number around 0.01.

Pressure spectra shift to lower frequencies away from the centerline.

Shock foot exhibits coherent to-and-fro motion up to a Strouhal number of 0.015.

Abstract

The dynamics of shock-induced unsteady separated flow past a three-dimensional square-faced protuberance is investigated through wind tunnel experiments. Time-resolved schlieren imaging and unsteady surface pressure measurements are the diagnostics employed. Dynamic Mode Decomposition (DMD) of schlieren snapshots, and analysis of spectrum and correlations in pressure data are used to characterize and resolve the flow physics. The mean shock foot in the centreline is found to exhibit a Strouhal number of around 0.01, which is also the order of magnitude of the Strouhal numbers reported in the literature for two-dimensional shock-boundary layer interactions. The wall pressure spectra, in general, shift towards lower frequencies as we move away from (spanwise) centreline with some variation in the nature of peaks. The cross-correlation analysis depicts the strong dependence of the mean shock oscillations to the plateau region, and disturbances are found to travel upstream from inside the separation bubble. Good coherence is observed between the spanwise mean shock foot locations till a strouhal number of about 0.015 indicating that the 3-D shock foot largely moves to-and-fro in a coherent fashion.