Turbulent statistics and flow structures in spanwise-rotating turbulent plane Couette flows

A series of direct numerical simulations of spanwise-rotating turbulent plane Couette flows at a Reynolds number of 1300 with rotation numbers Ro between 0 and 0.9 is carried out to investigate the effects of anticyclonic rotation on turbulent statistics and flow structures. Several typical turbulent statistics are presented, including the mean shear rate at the centerline, the wall-friction Reynolds number, and volume-averaged kinetic energies with respect to the secondary flowfield, turbulent field, and total fluctuation field. Our results show that the rotation changes these quantities in different manners. Volume-averaged balance equations for kinetic energy are analyzed and it turns out that the interaction term acts as a kinetic energy bridge that transfers energy from the secondary flow to the turbulent fluctuations. Several typical flow regimes are identified based on the correlation functions across the whole channel and flow visualizations. The two-dimensional roll cells are observed at weak rotation Ro = 0.01, where alternant clustering of vortices appears. Three-dimensional roll cells emerge around Ro approximate to 0.02, where the clustering of vortices shows the meandering and bifurcating behavior. For moderate rotation 0.07 less than or similar to Ro less than or similar to 0.36, well-organized structures are observed, where the herringbonelike vortices are clustered between streaks from the top view of three-dimensional flow visualization and form annuluses. More importantly, the vortices are rather confined to one side of the walls when Ro <= 0.02 and are inclined from the bottom to upper walls when Ro >= 0.07.