Numerical investigation of film cooling fluid flow and heat transfer using large eddy simulations

Large eddy simulations of film cooling from discrete holes inclined at 35° with a feeding plenum chamber are performed at a density ratio of 2 and blowing ratios from 0.5 to 2.0 in order to gauge the suitability and performance of different hole shapes. Cylindrical holes at length to diameter ratios of 1.75 and 3.5 as well as shaped holes (laterally diffused and console holes) at a length to diameter ratio of 3.5 are simulated issuing into a laminar crossflow at a Reynolds number of approximately 16,000 based on freestream velocity and hole diameter. The domain extends 15 hole diameters downstream of a single coolant hole, and periodic boundary conditions on the lateral faces of the domain are used. The results are validated in terms of the flow field and surface adiabatic effectiveness to experiments for cylindrical hole cases. Horseshoe vortices, DSSN vortices, and hairpin vortices are resolved and isolated. Jetting is found to have significant effects on effectiveness in cylindrical hole cases (with less jetting at the exit plane and better cooling performance from the longer holes) and shaped hole cases (with a laterally split jetting action occurring around a central recirculation region). The performance of the shaped holes is dramatically better than the performance of the cylindrical holes in terms of surface adiabatic effectiveness, with the console holes performing slightly better than the laterally diffused holes. In terms of aerodynamic loss, the console and cylindrical hole far outperformed the laterally diffused hole