Compound Triple Jets Film Cooling Improvements via Velocity and Density Ratios: Large Eddy Simulation

The flow hydrodynamic effects and film cooling effectiveness placing two small coolant ports just upstream the main jet (combined triple jets) were numerically investigated. Cross sections of all jets are rectangular and they are inclined normally into the hot cross-flow. The finite volume method and the SIMPLE algorithm on a multiblock nonuniform staggered grid were applied. The large-eddy simulation approach with three different subgrid scale models was used. The obtained results showed that this flow configuration reduces the mixing between the freestream and the coolant jets and hence provides considerable improvements in film cooling effectiveness (both centerline and spanwise averaged effectiveness). Moreover, the effects of density and velocity differences between the jets and cross-flow and between each of the jets were investigated. The related results showed that any increase in density ratio will increase the penetration of the jet into the cross-flow, but increasing the density ratio also increases the centerline and spanwise average film cooling effectiveness. Increasing the smaller jet velocity ratios, compared with the main jet, significantly improve the cooling effectiveness and uniform coolant distribution over the surface by keeping the main jet coolant fluid very close to the wall.