Numerical Investigation of a Film-Cooling Flow Structure: Effect of Crossflow Turbulence

Numerical simulation results using large-eddy simulation of a flow configuration relevant to the film cooling of turbine blades are presented. The flow configuration and the simulation parameters are chosen according to an experiment from literature, in which a hot turbulent crossflow over a flat plate is cooled by fluid issuing from a large isobaric plenum through a short inclined circular nozzle. Special attention is paid to the flow structure within the jet nozzle and the mixing region, as well as to the effect of the crossflow fluctuations thereon. To this end, the numerical results with the turbulent crossflow are compared to our previous data obtained with a steady mean-turbulent inflow profile. While the flow inside the nozzle is very similar for the two cases, large differences occur in the mixing region, where a much enhanced spreading of the coolant is observed with the turbulent crossflow. Consequently, the good agreement of the film-cooling efficiencies with the experimental data for the turbulent-crossflow case is contrasted by large deviations with the stationary inflow due to the lack of crossflow fluctuations.