Direct numerical simulations of rotating turbulent channel flow

Fully developed rotating turbulent channel flow has been studied, through direct numerical simulations, for the complete range of rotation numbers for which the flow is turbulent. The present investigation suggests that complete flow laminarization occurs at a rotation number Ro = 2 Omega delta/U(b) <= 3.0, where Omega denotes the system rotation, U(b) is the mean bulk velocity and 3 is the half-width of the channel. Simulations were performed for ten different rotation numbers in the range 0.98 to 2.49 and complemented with earlier simulations (done in our group) for lower values of Ro. The friction Reynolds number Re(tau) = u(tau)delta/v (where u(tau) is the wall-shear velocity and v is the kinematic viscosity) was chosen as 180 for these simulations. A striking feature of rotating channel flow is the division into a turbulent (unstable) and an almost laminarized (stable) side. The relatively distinct interface between these two regions was found to be maintained by a balance where negative turbulence production plays an important role. The maximum difference in wall-shear stress between the two sides was found to occur for a rotation number of about 0.5. The bulk flow was found to monotonically increase with increasing rotation number and reach a value (for Re(tau) = 180) at the laminar limit (Ro = 3.0) four times that of the non-rotating case.