Evaluation of the MIX-μ_t turbulent viscosity correction method for Reynolds-averaged Navier–Stokes predictions on trailing edge cutback film cooling

Trailing-edge cutback cooling is widely used in turbine blades because of its favorable aerodynamic performance. However, conventional Reynolds-averaged Navier–Stokes (RANS) models often fail to accurately predict cutback cooling effectiveness, mainly because they cannot resolve the unsteady mixing process dominated by lip-shedding vortices. The applicability of the MIX-μ_t turbulent viscosity correction method, originally proposed for film hole cooling, to trailing-edge cutback cooling is evaluated. By adjusting the turbulent Schmidt number and empirical correction parameters, the influence of this method on RANS prediction accuracy is assessed. The results show that turbulent viscosity correction can significantly improve the prediction of trailing-edge film cooling effectiveness. Without correcting the turbulent viscosity, adjusting only the turbulent Schmidt number cannot provide a consistent improvement under different blowing ratios. When the empirical parameter is set to 1.5, the model moderately enhances turbulent viscosity in the mainstream–coolant mixing region, thereby compensating for the underprediction of unsteady mixing caused by lip-shedding vortices and shear layer entrainment in steady RANS simulations. This parameter is calibrated using pressure-sensitive-paint data for a smooth trailing edge at blowing ratios of 0.25 and 0.50 with a density ratio of 1.0, yielding maximum deviations of 5.5% and 3.5%, respectively, in terms of the spanwise-averaged film cooling effectiveness. Further verification is obtained for the straight-ribbed trailing edge with a blowing ratio of 0.50 and the literature trailing-edge configurations with blowing ratios of 0.40 and 1.0–1.5. Nevertheless, the physical mechanisms and universality of the optimized parameters require further investigation.