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Film cooling is widely applied as an effective way to maintain the turbine blade temperature at an acceptable level. The present paper investigates the overall cooling effectiveness and flow structure by performing conjugate heat transfer simulations for the flat-plate baseline cylindrical and three cratered film-cooling holes. The flow and heat transfer in the fluid domain is obtained using the Shear Stress Transport turbulence model, and the solid conductivity is considered by solving the Laplace equation. Four blowing ratios ranging from 0.5 to 2.0 are studied. The numerical results show that the concentric elliptic cratered hole yields a slightly higher overall cooling effectiveness than the baseline cylindrical hole, but the two contoured cratered holes exhibit great improvements due to the generation of the anti-kidney-shaped vortex pair. The area-averaged overall cooling effectiveness has improved by 5.58–65.30% for the contoured cratered hole. The variation of Biot number results in small change in the area-averaged overall cooling effectiveness. However, the area-averaged overall cooling effectiveness uniformity coefficient depends on the Biot number.

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The cooling performances for the cylindrical film-cooling hole with divided downstream crescent-shaped blocks were numerically investigated in present study. Four configurations with divided crescent-shaped block, i.e. linear, 30° convergence, 30° expansion, and 30° curved expansion, were studied at typical flow conditions. The successive crescent-shaped block case and the no block case were also solved in comparison. The temperature profiles, the local and lateral averaged cooling effectiveness at blowing ratios of 0.5 to 1.5 were obtained. As compared with the successive block case, the lateral coolant coverage were widened by using the divided block, and thus the lateral averaged cooling effectiveness were improved, especially at higher blowing ratios. Comparatively, the cylindrical hole with 30° expansion crescent-shaped block exhibited highest cooling performance.