Development of an Improved K-Tau Model for Film Cooling Applications

An improved two equation model of turbulence has been developed with the objective of applying it to predicting the turbine blade film cooling problem. The model employs an equation for the turbulent time scale, tau, instead of the epsilon equation and thereby eliminates the ad-hoc prescription of boundary conditions as well as the anomalous behavior of epsilon in the close proximity of a wall. Asymptotically consistent near wall damping functions have been developed and a two-layer approach has been employed to prescribe the near-wall behavior of the turbulent time scale, tau. The model thus developed, has been validated for wall bounded non-recirculating as well as recirculating flows and has also been tested for wall-free shear flow, showing improved predictions. A detailed and systematic, step-by-step development of the model along with validation results is being presented in this study.