Low Reynolds number effects on rotating turbulent Poiseuille flow

Direct numerical simulations with a spectral method are performed to study the effects of spanwise rotation on a turbulent Poiseuille flow at very low Reynolds number. At this Reynolds number, the region of zero absolute vorticity, typically observed in the mean velocity profile of rotating Poiseuille flow, disappears in the channel center, and the mean velocity gradient becomes opposite to that of zero absolute vorticity. When zero absolute vorticity disappears, very long low-speed streaks, accompanied by the vortices aligned in the streamwise direction like a chain, dominate the flow, in which the transfer of turbulent kinetic energy into the vicinity of the wall and small-scale streamwise vortices disappear there. However, low-speed fluids are pumped up from the near-wall region, and trapped into the channel center by the larger-scale chain vortices away from the wall, which decreases the mean velocity in the channel center and shifts its peak location toward the wall.