Impact of inflow turbulence on large-eddy simulation of film cooling flows

The paper investigates the impact of industrially appropriate inflow turbulence on the turbulent state, mixing capability and surface coolant distribution of film cooling flow using LES. Near-wall and freestream turbulence, corresponding to turbulent boundary layers and stochastic turbulent fluctuations away from the wall, have been investigated. In our study, we set up three main test scenarios: no inflow turbulence, near-wall boundary layer turbulence and freestream turbulence. Our work shows that surface adiabatic cooling effectiveness differs significantly with and without inflow turbulence. It is also evident that freestream turbulence enhances the mixing ability of a cooling flow, providing an initial enhance- ment of surface cooling close to the hole but with reduced cooling effectiveness downstream. Turbulent length scales, turbulent heat flux and turbulent anisotropy are compared and illustrate the changes in cooling effectiveness as a result of the upstream turbulent behaviour. As a result, despite inflow turbu- lence being a complex subject and problem-dependent, the importance of introducing realistic turbulent inflow in LES of cooling flows is demonstrated.