Effects of diameter ratio and inclination angle on flow and heat transfer characteristics of sister holes film cooling

In order to investigate the flow and heat transfer characteristics of sister holes cooling method, sister holes cooling structures have been applied on a flat plate with four primary to sister hole diameter ratios and three inclination angles under three blowing ratios. Single cylindrical hole film cooling structure is also established as a benchmark structure. The numerical results of the single cylindrical hole case and one sister holes case are validated with the experimental results available in literatures. The tangential velocity vectors and total vorticity distributions are studied and compared. The spanwise averaged film cooling effectiveness and the adiabatic temperature contours are studied and compared. Results show that the development of the kidney vortex induced by primary hole is impeded by the sister hole induced kidney vortex and thus the film cooling performance is promoted. The blowing ratio and diameter ratio heavily affect the flow and heat transfer characteristics of sister holes cooling cases, the influence of the inclination angle is much smaller. In this paper, the best film cooling performance of sister holes cooling cases is obtained under the smallest diameter ratio.