Unsteady mechanisms in shock wave and boundary layer interactions over a forward-facing step

The flow over a forward-facing step (FFS) at $Ma_\infty =1.7$ and $Re_{\delta _0}=1.3718\times 10^{4}$ is investigated by well-resolved large-eddy simulation. To investigate effects of upstream structures turbulence on the low-frequency dynamics shock wave/boundary layer interaction (SWBLI), two cases are considered: one with laminar inflow turbulent inflow. case shows signs rapid transition to step, as inferred from streamwise variation $\langle C_f \rangle$ evolution coherent vortical structures. Nevertheless, separation length more than twice large for case, coalescence compression waves into observed only fully case. low medium frequencies characterized spectral analysis, where lower frequency range related unsteady region, intermediate associated shedding shear vortices. For we furthermore use three-dimensional dynamic mode decomposition analyse individual contributions selected modes unsteadiness SWBLI. Görtler-like vortices, which induced centrifugal forces in strongly correlated current FFS Similarly previously backward-facing steps, observe slightly higher non-dimensional (based length) SWBLI flat plate ramp configurations.