Impact of inflow turbulence on large‐eddy simulation of film cooling flows.

• Film cooling effectiveness is highly dependant on upstream turbulence conditions. • Upstream turbulent boundary layer fluctuations are a key factor in promoting lateral coolant spread. • Upstream turbulent boundary layer fluctuations suppress laminar shear layer stabilities in the coolant-hot gas mixing layer. • Coolant hole flow dominates smaller scale turbulence in the near-wall region close to the coolant hole trailing edge. • High FST intensity flow shows increased integral length scales in the coolant jet compared to near-wall and no inflow turbulence cases. 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 enhancement 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 turbulence being a complex subject and problem-dependent, the importance of introducing realistic turbulent inflow in LES of cooling flows is demonstrated. [ABSTRACT FROM AUTHOR]