Effect of film cooling injection on downstream heat transfer coefficients in high speed flow

An experimental and theoretical investigation was performed to examine the effect of film cooling injection from a two-dimensional slot on the downstream surface heat transfer. The coolant gas was ejected normal to the wall from a porous section on a flat plate under a supersonic Mack 3 mainstream. The mass velocity of injection was 1 percent to 2 percent of the mainstream value and resulted in decreases of 10 percent to 20 percent in the heat transfer coefficients near the slot. A simple theoretical model was formulated which accounted for the effect of the injection on thickening the boundary layer, and which accurately predicted the moderate decreases in heat transfer coefficients observed in the experiments.