Analysis of low-frequency unsteadiness in the direct numerical simulation of a shockwave and turbulent boundary layer interaction”, AIAA Paper No

The direct numerical simulation (DNS) of a compression ramp shockwave and turbulent boundary layer interaction (STBLI) is presented. The incoming ow conditions are Mach 2.9 and Re 2900. The ramp angle is 24 . The dominant time scales in the ow are inferred from a spectral analysis of pressure signals along the wall, and pressure and mass ux signals in the ow. The low-frequency shock motion in the DNS is broadband with a dominant frequency of approximately 900Hz, which is two orders of magnitude lower than the characteristic frequency of the turbulence in the incoming boundary layer. The present DNS is signicantly longer in time than a previous DNS1 and covers close to ten periods of the low-frequency unsteadiness (based on the dominant frequency). We also determine the statistical link between the shock motion and the uctuations in the downstream, separated ow. Nomenclature 99 % boundary layer thickness displacement thickness density momentum thickness Cf skin-friction coecient f lter function (or frequency) i; j; k computational coordinate in the streamwise, spanwise and wall-normal directions Lsep length of separated region M Mach number p pressure Re Reynolds number based on the momentum thickness, Re Reynolds number based on the displacement thickness, T temperature u; v; w streamwise, spanwise and wall-normal velocity x; y; z streamwise, spanwise and wall-normal coordinate Subscripts 1 freestream quantity w wall quantity I