  The present work reports on the flow physics of turbulent supersonic flow
over backward facing step (BFS) at Mach 2 using LES methodology where the
dynamic Smagorinsky model is used for SGS modeling, while POD is invoked to
identify the coherent structures present in the flow. The mean data obtained
through the computations is in good agreement with the experimental
measurements, while the iso-surfaces of Q-criterion at different time instants
show the complex flow structures. The presence of counter rotating vortex pair
in the shear layer along with the complex shock wave/boundary layer interaction
leading to the separation of boundary layer is also evident from the contours
of both Q and the modulus of vorticity. Further, the POD analysis reveals the
presence of coherent structures, where the first and second modes confirm the
vortical structures near the step as well as along the shear layer in the
downstream region; while the second, third and fourth modes confirm the
presence of vortices along the shear layer due to Kelvin-Helmholtz (K-H)
instability. Moreover, POD as well as frequency analysis is extended at
different planes to extract the detailed flow features.
