Prediction of longitudinal roll cells in rotating plane turbulent Couette flow

The ability of a second-moment closure to predict the three-componential me an flow which results when a plane Couette flow is subjected to moderate an ticyclonic system rotation is explored. The counterrotating streamwise-orie nted roll cells, which may occur by the imposition of a destabilizing Corio lis force field, are treated as an integral part of the steady mean motion governed by the Reynolds-averaged Navier-Stokes equations. Near-wall effect s are accounted for by Durbin's elliptic relaxation approach, while system rotation only appears naturally in rotational stress-producing terms and in the mean intrinsic vorticity in the non-linear pressure-strain model. The model predictions mimicked the most striking effects of anticyclonic ro tation, as observed in a series of recent direct numerical simulations. In particular they reproduced the characteristic energetic roll-cell pattern, which inevitably enhanced the cross-sectional mixing. The broadening of the central core region, in which the primary mean velocity profile adjusted i tself to make the absolute mean vorticity negligibly small, was well captur ed by the predictions, together with the remarkable damping of the turbulen t velocity fluctuations. The success of the predictions supports the view t hat such large-scale structures as the rotational-induced roll cells should be treated as a part of the resolved mean flow field, the obvious and phys ically appealing implication being that the turbulence closure is left to r epresent nothing but real turbulence.