Experimental Study on the Film-Cooling Characteristics of the Cylindrical Holes Embedded in Sine-Wave Shaped Trench

An experimental investigation has been performed to study the film-cooling performance of the cylindrical holes embedded in the sine-wave-shaped-trench. The sine-wave-shaped-trench is obtained by changing the trailing edge of the transverse trench into sine-wave shape; the holes are located next to the peaks of the wave. The sine-wave-shaped-trench is expected to get a wider spread of the cooling jet in the spanwise direction. The film-cooling effectiveness, heat-transfer coefficient, and discharge coefficient of the sine-wave-shaped-trench hole configurations with different trench depths (0.75D, 1D) and wave peaks (1D, 2D) are measured by the transient thermal liquid measurement technique. The blowing ratio covers a range from 0.5 to 2.0. The transverse trench hole is investigated as a basis of the comparison. Thermal and hydrodynamic fields are investigated numerically using Reynolds-averaged Navier-Stokes (RANS) simulations with Realizable k-ϵ turbulence model and enhanced wall treatment. Results show that broadening the wave peak of the sine-wave-shaped-trench improves the spanwise uniformity of the injection. There is a pair of anticounter-rotating vortices formed downstream of the sine-wave-trailing-edge. Increasing the trench depth shows positive effects on the heat-transfer coefficients ratio of the sine-wave-shaped-trench. The discharge coefficients of the sine-wave-shaped-trenches are higher than that of the transverse trench which means the sine-wave shape trench has a lower flow resistance.