Numerical simulation and aerothermal physics of leading edge film cooling

A viscous flow solver based on the Runge-Kutta scheme has been modified for the numerical investigation of the aerothermal field due to the leading edge film cooling at a compound angle. An existing code has been modified to incorporate multiblock capabilities. Good agreement with the measured data has been achieved. The results of the numerical investigation have been used to analyse the vortex structure associated with the coolant jet-free-stream interaction to understand the contribution of different vortices on the cooling effectiveness and aerothermal losses. Two counter-rotating vortices generated by the interaction between the main flow and the coolant jet have been found to have a major influence in decreasing the cooling efficiency through strong entrainment of the hot fluid. Numerical simulation was carried out to investigate the influence of the inlet Mach number, the inlet turbulence intensity and the length scale on the aerothermal field due to the leading edge film cooling. Variation in the inlet Mach number leads to a minor modification of the cooling effectiveness, and this is predominantly caused by the modified pressure gradient. An increased turbulence intensity has a profound effect on the cooling near the leading edge. The adiabatic effectiveness downstream of the second row of coolant holes is less sensitive to a change in the turbulence intensity. The results of the numerical simulation indicate that the turbulence length scale has a significant effect on the accuracy of the numerical prediction of film cooling. Not only the inlet turbulence intensity but also the turbulence length scale should be accurately set to achieve a reliable numerical prediction of the heat and mass transfer due to film cooling.