There you go..
During earlier research on shock wave/boundary layer interaction control, the effect of air humidity on flow separation has been observed. This has inspired a more detailed study on the effect of air humidity on shock induced incipient separation and on the involved processes. The phenomenon has a twofold nature. In supersonic flow, the condensation of humidity causes flow retardation due to heat addition. The consequent weakening of the shock wave reduces the tendency towards separation. On the other hand, the incipient separation is postponed at the same Mach numbers of interaction.
No, I don't understand it either.
