Unsteady wall blowing and suction has been a traditional approach for boundary-layer transition control. Previous results showed that the synchronization point of mode S and mode F plays an important role in transition control using wall blowing and suction. In this paper, numerical simulations are conducted to study the effect of steady blowing and suction on the modal growth of a Mach 5.92 flat-plate boundary layer. The steady base flow is firstly simulated by solving compressible Navier-Stokes equations. Stability characteristics of boundary-layer waves are analyzed by linear stability theory (LST). In stability simulations, two-dimensional disturbances corresponding to mode S at the frequency of 100 kHz is introduced near the leading edge of the flat plate. Steady blowing and suction of various location, amplitude, and profile is imposed to investigate its effect on the growth of mode S. The results show that, in general, D-typc blowing and suction stabilizes mode S when it is imposed upstream of the synchronizaiton point. When steady blowing and suction is imposed downstream of the synchronization point, K-typc blowing and suction generally stabilzcs mode S.
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