Film Cooling Performance of the Staggered Arrangement of Auxiliary Holes and Main Holes on a Flat Plate

The film cooling effectiveness of a staggered arrangement of small and large holes was investigated. The small auxiliary holes were located normal to the cooled surface, whereas the large main holes had an inclination angle of 30°. The center points of the small holes were located upstream, downstream, and in the same position as the main holes. A hole pitch (P/D) of 3 and a thickness (t/D) of 3 were considered. The film cooling performance of the hole in trench structure and the cylindrical hole was also determined. The numerical results show that large-scale vortices caused by the auxiliary hole injection inhibit the development of vortices caused by the main hole in the streamwise direction. This result differs from that of anti-vortex film cooling. Compared to the baseline, the increase in the surface-averaged values is 15-22% for the staggered arrangement, depending on the blowing ratio (0.5 to 2.0). The positions of the auxiliary holes have an effect on the spanwise-averaged values.