Film Cooling Effectiveness Enhancement Applying another Jet in the Upstream Neighbor of the Main Jet-Using LES Approach

Flow hydrodynamic effects and film cooling effectiveness of placing a coolant port (upstream jet) just; upstream of the main cooling jet were numerically investigated. The upstream jet was added such that the; total cooling cross section (cross sections of the main and upstream jets) remains constant, in comparison to; the case of ordinary cooling jet. The finite volume method and the unsteady SIMPLE algorithm on a multiblock nonuniform staggered grid arrangement were applied. The large eddy simulation (LES) approach with; the one equation subgrid scale model was used. The jet to cross flow velocity ratio (for both of the main and; the upstream jets) is 0.5 and the cross flow Reynolds number (based on the main jet parameters) is equal to; 4700. The obtained results showed a significant improvement in the flow control capability and both; centerline and spanwise averaged film cooling effectiveness applying the new cooling configuration. Effects; of the upstream jet dimensions are also studied here. The obtained results showed that the spanwise width of; the upstream jet has more essential influence on the cooling performance than that of its streamwise width.; Moreover, it is demonstrated that the film cooling performance could be enhanced even by applying an; upstream jet which its temperature is as same as the crossflow temperature, i.e. applying a hot upstream jet.; Finally, it is shown that presence of the upstream jet decreases the streamwise component of the velocity; near the wall, which decreases the wall shear stress and the skin friction drag coefficient significantly.