Laminarization of inhomogeneous turbulent channel flow under stable density stratification

Abstract

Effects of buoyancy force stabilizing the disturbances are investigated on a turbulent channel flow bounded by two walls of different temperatures. With a constant mean pressure gradient imposed, the buoyancy force related to the Grashof number (Gr) is systematically increased by increasing the temperature difference between upper and lower walls, which are perpendicular to the gravitational direction. As a result, the mean flow rate increases with an increase in the Gr, and turbulent structures become intermittent and inhomogeneous; turbulent and quasilaminar regions simultaneously appear in the same computational region. Detailed visualization for instantaneous turbulent structure shows that in the upper and lower sides of a channel, the turbulent regions appear alternatively, and local one-sided turbulence is observed. Finally, with a further increase in the Gr, the stratified channel flow becomes complete one-sided turbulence where a flow becomes turbulent on one side of a channel, while it becomes laminarized on the other side.