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Abstract. In the modern gas turbine, film cooling system was applied to the turbine blades to provide thermal protection from extreme turbine inlet temperatures. Recent literature discovers that adding the double flow control device (DFCD) and combining two cylindrical holes (combinedhole) are the ways to further enhance the film cooling performances. In the present simulation work, the influence of DFCD on the combined-hole film cooling was investigated at different blowing ratios. The comparison between two different computational domains of combined-hole film cooling with and without DFCD was further discussed in the present work. The results show that increase the blowing ratio, M rise the overall performance of combined-hole film cooling with and without DFCD. Based on the different computational domain, combined-hole with DFCD has better lateral spread at M = 0.5 and M = 0.75 in comparison with the combined-hole without DFCD. However, due to large counter clockwise vortex produced by the combined-hole with DFCD, unsymmetrical film cooling coverage was formed along the streamwise direction at M = 1.0 and M =1.5. As the conclusion, combined-hole film cooling with DFCD has better performance at M = 0.5 and M = 0.75 while combined-hole film cooling without DFCD has better performance at high blowing ratio of M = 1.0 and M = 1.5.

The present work describes the airflow characteristics upstream and downstream of the circular orifice numerically using the standard k-ε model and RSM and experimentally employing hot-wire and Pitot tube devices to measure the flow velocities through a tube. An expectation has to bear in mind; the RSM performed well and predicted results in a good level of agreement against the experimental measurements found in preceding studies and the present experimental data as well. In terms of flow physics point of view, velocity and turbulent kinetic energy distribution are presented. Moreover, turbulent viscosity, Reynolds stresses (u2, v2, w2) are also considered. Furthermore, the contours of velocity, static pressure and turbulent kinetic energy are presented beside the wall shear stress and y+ profiles are illustrated to show the flow physics as well as to compare the results of two different turbulence models considered in this study employing Reynolds of 30000 and the ratio of orifice diameter to the pipe diameter of 0.5.

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