  We perform direct numerical simulations of shock-wave/boundary-layer
interactions (SBLI) at Mach number M = 1.7 to investigate the influence of the
state of the incoming boundary layer on the interaction properties. We
reproduce and extend the flow conditions of the experiments performed by
Giepman et al., in which a spatially evolving laminar boundary layer over a
flat plate is initially tripped by an array of distributed roughness elements
and impinged further downstream by an oblique shock wave. Four SBLI cases are
considered, based on two different shock impingement locations along the
streamwise direction, corresponding to transitional and turbulent interactions,
and two different shock strengths, corresponding to flow deflection angles 3
degreees and 6 degrees. We find that, for all flow cases, shock induced
separation is not observed, the boundary layer remains attached for the 3
degrees case and close to incipient separation for the 6 degrees case,
independent of the state of the incoming boundary layer. The findings of this
work suggest that a transitional interaction might be the optimal solution for
practical SBLI applications, as it removes the large separation bubble typical
of laminar interactions and reduces the extent of the high-friction region
associated with an incoming turbulent boundary layer.
