- The effect of injection hole geometry on the leading edge heat transfer coefficient and film cooling effectiveness, under high mainstream turbulence condition, was experimentally studied for an incident mainstream Reynolds number of 100 000. Data were obtained for three blowing ratios of 0.4, 0.8 and 1.2 through two rows of film holes located at 15 and 40 for two injection geometries: (a) film holes spaced four hole diameters apart and (b) film holes spaced three hole diameters apart, in the spanwise direction. The results show that the leading edge heat transfer coefficient increases and the film effectiveness decreases with increasing mainstream turbulence; however, the effect reduces with increasing blowing ratio. The leading edge heat transfer with coolant injection (heat load) for the three hole diameters case is lower than that for the four hole diameters case at low mainstream turbulence, but the difference reduces at higher mainstream turbulence. 1992.