Analysis of Flow Physics and Jet-Mainstream Interaction in Leading Edge Filmcooling Using Large Eddy Simulation

A numerical investigation is conducted to study leading edge film cooling at a compound angle with Large Eddy Simulation (LES). The domain geometry is adopted from an experimental set-up (Ekkad et al. [14]) where turbine blade leading edge is represented by a semi-cylindrical blunt body. The leading edge has two rows of coolant holes located at ±15° of the stagnation line. Coolant jets are injected into the flow field at 30° (spanwise) and 90° (streamwise). Reynolds number of the mainstream is 100,000 and jet to mainstream velocity and density ratios are 0.4 and 1.0, respectively. The results show the existence of an asymmetric counter-rotating vortex pair in the immediate wake of the coolant jet. In addition to these primary structures, vortex tubes on the windward side of the jet are convected downstream over and to the aft- and fore-side of the counter-rotating vortex pair. All these structures play a role in the mixing of mainstream fluid with the coolant. A turbulent boundary layer forms within 2 jet diameters downstream of the jet. A characteristic low frequency interaction between the jet and the mainstream is identified at a non-dimensional frequency between 0.79 and 0.95 based on jet diameter and velocity. The spanwise averaged adiabatic effectiveness agrees well with the experiments when fully-developed turbulence is used to provide time-dependent boundary conditions at the jet inlet, without which the calculated effectiveness is overpredicted.