Two-dimensional Navier-Stokes equation was numerically solved to reproduce dynamics of a flow separation under supersonic flow with Mach number of 1.7. The repetitive pulses were irradiated to the under surface of the diamond wing to control the flow separation induced on the upper surface. A strong blast wave was generated from a focal point of the repetitive pulses because of a rapid gas heating. The expansion wave was induced from the trailing edge when the blast wave with the supersonic speed propagated from the under to upper surfaces. The separation region on the upper surface became smaller by irradiating the repetitive pulses on the under surface because the expansion wave induced from the trailing edge interacted with a recompres-sion wave and relaxed an inverse pressure gradient on the upper surface. A lift-to-drag ratio of the wing was improved by utilizing an energy deposition of the repetitive pulses because of a decrease in the pressure on the upper surface and an increase in the pressure on the under surface. An effectiveness of a “contactless” flow control device using the repetitive pulses was revealed by our numerical simulation.