The effect of holes shape on film cooling was investigated numerically in the present study. Three cases of holes which are sister holes located in the downstream (case 1), upstream (case 2) and side (case 3) were studied when keeping the flow area and flow rate constant. Cylindrical hole was also investigated to make a comparison. The results showed film cooling effectiveness is higher at the blowing ratio M = 0.5 for cylindrical hole; while for the hole with sister holes, film cooling performance is better at corresponding blowing ratio M = 1.0 and it is better than that of the cylindrical hole. The reason is that the interaction between the mainstream and the cooling stream produces the counter-rotating vortex pairs (CVP) at high blowing ratio, which will make the hot mainstream underneath the cooling stream and lifts the cooling stream from the surface for the cylindrical hole. And the three cases of holes with sister holes can weaken the effect of the CVP.

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