Influence of periodic pulsations on separation induced by shock wave–boundary layer interaction

Shock wave–boundary layer interaction in a duct is investigated via large eddy simulation to understand the effects of strong pulsations induced by blade row interaction in highly loaded turbomachinery. Periodic inlet total pressure pulsations with varying frequencies are imposed at the inlet. Numerical results show that the separation bubble, induced by the interaction between the shock wave and the boundary layer, is suppressed under the influence of the imposed pulsations. The suppression effect varies with frequency, with a maximum reduction in the time-averaged separation bubble length reaching approximately 10%. Spectral analyses reveal that vortex shedding and breakdown behavior in the shear layer are modulated by the imposed pulsations. At specific forcing frequencies, large-scale unsteady motions become fully synchronized with the pulsations. Further analysis of turbulence statistics shows that peak turbulent kinetic energy in the shear layer increases under pulsations, indicating enhanced turbulence intensity. This leads to stronger momentum exchange between the core flow and the separation bubble, thereby promoting separation suppression. These findings provide new insights into how periodic pulsations can control shock–boundary layer interactions. This study could inspire the development of unsteady flow control technologies, such as plasma-based or pulsed jet techniques, for separation control in high-load compressors by targeting the unsteady characteristics of the near-wall shear layer.