Prediction of Turbulent Channel Flows with Spanwise, Streamwise and Wall-normal Rotations.

Abstract

Turbulent channel flows rotating about the spanwise, streamwise and wall-normal axes are calculated with a low-Reynolds-number second-moment closure. The stabilizing and destabilizing effects of the spanwise rotation are reproduced by the model due to the exact stress production term related to the rotation. In the case of weak streamwise rotation, a shear stress component induced by the rotaion changes its sign at a position between the wall and the centerline. This feature is captured by the model and the predicted velocity profiles are in reasonable agreement with DNS data. At high rotation rates, however, the sign reversal disappears in DNS and the predicted sign disagrees with that of DNS almost over the whole region, leading to poor predictions of the velocity profiles. The budget of the stress component suggests a need for a redistribution process which works against the exact rotation production. The wall-normal rotation directly affects the mean flow field. This rotation leads to relaminarization of the flow when the rotation rate becomes high. Good predictions are obtained for weak rotation but the model gives relaminarization at a lower rotation number than DNS.