Comparison of Three Different Two-equation Turbulence Models in Predicting Narrow Trench Film Cooling Effectiveness

摘要

In this study, three turbulence models k-ε, standard k-ω and SST Gamma Theta which all available in ANSYS CFX were used. Gamma Theta Model is the recommended transition model for general-purpose applications. The full transition model is based on two transport equations, one for the intermittency and one for the transition onset criteria in terms of momentum thickness Reynolds number. Narrow trench configuration is used to predict the improvements in film cooling performance. Blowing ratios in the range (0.5, 1 and 1.4) were investigated. The results compared with experiments at different blowing ratios. Comparison of results with the k-ε model indicates that each SST Gamma Theta and k-ω models predict circulations inside trench equally well at M=1. Over the surface, at low blowing ratios all models in case lateral spreading are under predicted, but SST Gamma Theta model shows some improvements in prediction than k-ω. At high blowing ratios, SST Gamma Theta model offers good prediction in centerline with experiment than others, but all models show under predicted in lateral direction.