Causality in the shock wave/turbulent boundary layer interaction

What drives flow unsteadiness in the shock wave/turbulent boundary layer interaction? Two mechanisms are widely recognized to play a role this problem: upstream forcing and downstream feedback. In work, through combined use of system identification, spectral decomposition, linear stability analysis, we demonstrate that feedback, driven by traveling acoustic waves, is dominant mechanism behind low-frequency motion. The tools described herein enable an accurate reconstruction fluctuations could find potential applications active control.