Numerical investigation of different turbulence models applied in combined impingement and film cooling

Numerical investigations of combined impingement and film cooling based on different turbulence models have been carried out and compared in the present study. The specific test case combines the complex flow physics of the jet impinging, turning and subsequent mixing with hot mainstream, which consists of jet shear layer separation, wall boundary layer transition, coolant jet detachment and reattachment. The turbulence models employed are the k  − standard, RNG, and realizable models, the k − standard, SST, and Transition SST models, and the t l k − k − model. Numerical tests have been performed at three representative blowing ratios from low to high for each turbulence model. The computed cooling effectiveness from  equation models tend to be underpredicted at low blowing ratio while numerical profiles of cooling effectiveness achieve considerable agreement with the measured experiment data at moderate and high blowing ratios. In addition, the computed results from  equation models reasonably match the measured data at low blowing ratio but cooling effectiveness are markedly underpredicted at moderate and high blowing ratios. In contrast, those results from the t l k − k − model agree fairly well with those of the experiment at various blowing ratios. Owing to the nature description of the pre-transitional streamwise fluctuations in the laminar kinetic energy, the solutions from t l k − k − model clearly reveal the complex flow physics in the combined impinging and film cooling in the confined region, where the jet shear layer separation, boundary layer transition, coolant detachment and reattachment co-exist. However, the large number of specified parameters in the t l k − k − model still needs to be further optimized to reach the enhanced agreement with experimental data and obtain extensive applications for combined cooling schemes.