Numerical Simulation of Aerodynamic Losses in Flat-Plate Film Cooling Using Vortex Dynamics

Gas film cooling is a widely adopted technique for the thermal protection of gas turbine blades. However, a trade-off exists between reduced cooling effectiveness and increased aerodynamic losses. The underlying mechanism was investigated through large eddy simulation (LES) with the WALE subgrid-scale model, applied to a flat-plate, single-hole model. The flow characteristics, flow field structures, and aerodynamic loss generation mechanisms of circular, fan-shaped, and laterally expanded holes were systematically examined for blowing ratios ranging from 0.3 to 1.2. The results indicate that all three hole geometries provide adequate film coverage at low blowing ratios. At high blowing ratios, however, the cooling performance is degraded by jet penetration in the circular hole and flow recirculation within the fan-shaped hole. In contrast, the laterally expanded hole demonstrates superior film adhesion stability. In terms of aerodynamic loss, the circular and fan-shaped holes incur higher losses, whereas the laterally expanded hole exhibits the lowest loss under all conditions, which is attributed to its effective tangential momentum dispersion. This study elucidates the influences of orifice geometry and vortex structure evolution on both cooling effectiveness and aerodynamic loss, providing valuable insights for the optimization of gas film cooling design in gas turbines.