Abstract: A direct numerical simulation of shock wave and transitional boundary layer interaction for a 24 deg compression ramp at Mach 2.9 is conducted. The intricate flow phenomena in the ramp-corner, including coherent vortex structures, separation bubble characteristics and shock wave behaviors, have been studied systematically. The DNS results of transitional interaction are compared with the corresponding turbulent interaction and the reasons for the differences are analyzed. The evolution of the transitional boundary layer in the ramp is researched. The fluctuation of wall pressure and distribution of skin-friction coefficient in the transitional interaction are investigated in detail. Results indicate that the distribution of coherent vortex structures is non-uniform in the spanwise direction and the separation bubble is reduced to a V-shape by the mutual interactions of the hairpin vortices chains. The shock fronts are destroyed badly and even break down by the interaction. The multiple layer of shock foots is observed obviously. The interactions rapidly accelerate the evolution of transition and greatly amplify the intensity of fluctuations. The peak of wall pressure fluctuations appears with single-peak structure at the downstream of separation region. And the overshoot of skin friction induced by transitional interaction is explained by the strong Reynolds shear stress and high turbulent kinetic energy.

Key words: Transition, Coherent structures, Compression ramp, SWBLI, Direct numerical simulation