  The present numerical investigation uses well-resolved large-eddy simulations
to study the low-frequency unsteady motions observed in
shock-wave/turbulent-boundary-layer interactions. Details about the numerical
aspects of the simulations and the subsequent data analysis can be found in
three papers by the authors (Theo. Comput. Fluid Dyn., 23:79--107 (2009); Shock
Waves, 19(6):469--478 (2009) and J. of Fluid Mech. (2011)). The fluid dynamics
video illustrates the complexity of the interaction between a Mach 2.3
supersonic turbulent boundary layer and an oblique shock wave generated by a
8-degree wedge angle. The first part of the video highlights the propagation of
disturbances along the reflected shock due to the direct perturbation of the
shock foot by turbulence structures from the upstream boundary layer. The
second part of the video describes the observed block-like back-and-forth
motions of the reflected shock, focusing on timescales about two orders of
magnitude longer than the ones shown in the first part of video. This gives a
visual impression of the broadband and energetically-significant peak in the
wall-pressure spectrum at low frequencies. The background blue-white colouring
represents the temperature field (with white corresponding to hot) and one can
clearly appreciate why such low-frequency shock motions can lead to reduced
fatigue lifetimes and is detrimental to aeronautical applications.
