Prediction of Heat Transfer and Flow Transition on Transonic Turbine Airfoils Under High Freestream Turbulence

Accurate modeling of the laminar-turbulent transition remains a challenge for the prediction of external heat transfer on turbine airfoils. This paper presents a numerical study for turbine heat transfer and by-pass transition under high freestream turbulence using advanced turbulence models. Reynolds-Averaged Navier-Stokes (RANS) analyses have been carried out for two transonic turbine airfoils, with inlet turbulence intensity ranging from 12% to 16%, and exit Reynolds number varying from 8x10(5) to 1.5x10(6). The RANS results are compared against the recent data from Virginia Tech, as well as the predictions from a 2-D boundary layer code - TEXSTAN. The effects of inlet turbulence length scale on the freestream turbulence decay and boundary layer transition are investigated using different models, including a Reynolds stress model. It is found that a Postulation by Steelant and Dick can be used to set up plausible turbulence length scales at the inlet. h is observed that maintaining a proper decay rate of freestream turbulence inside the turbine passages is necessary to achieve reasonably good prediction of transition and heat transfer. The V2F, SST, and k-epsilon turbulence models have been assessed.