Large-scale structure alternation in rotating plane Poiseuille flow at transitional Reynolds number

We performed a series of direct numerical simulations of transitional rotating Poiseuille flow, employing a large computational domain and discussed alternations of large-scale structures, such as the turbulent stripe and roll cell. The structure of the turbulent stripe is a laminar-turbulent banded pattern and the roll cell has an array of longitudinal vortexes aligning regularly in the spanwise direction. We observed the occurrence of turbulent stripes only under a low-rotation condition and the roll cells under high rotation. In the intermediate region, we found a transitional state from a static to a rotating system, which involved the coexistence of turbulent stripes and roll cells. In this study, we examined the process of disappearance of turbulent stripes and of the development of turbulent diffusion. A small net drag reduction can be achieved when relaminalization occurs and the turbulent stripe disappears on the suction side, although the drag increases monotonically once the roll cell dominantly affects the flow on the pressure side.