Unstead 3-D heat transfer computations in rotor blade passages

Unsteady load predictions on turbine blades are needed for a better understanding of high cycle fatigue blade failures. The forced response due to rotor-stator interaction and the unsteady loads due to blade oscillatory motion are major factors for the cause of stresses. In addition, turbulence, which is generated through the rotor passages of a turbine, significantly affects the flow characteristics and heat transfer of the rotor blades. This study presents a numerical modeling of turbulence effects of a flow in a rotor blade passage using three-dimensional unsteady calculations due to blade oscillation. The computational results obtained using these models are compared in order to investigate the turbulence effect in the near-wall region. Both pressure coefficients and Stanton number were compared with the published experimental data. It is observed that the two turbulence models predict different results for the turbulence kinetic energy. This variation is identified as being related to some non-isotropic turbulence occurring near the blade surface due to the severe acceleration of the flow. It is thus proven that the models based on the RSM give more realistic predictions for highly turbulent cascade flow computations than the k-epsilon model.