Stratification effect on extreme-scale rolls in plane Couette flows

Abstract

[EN] The existence of the large-scale structures appearing in turbulent Couette flows is studied by means of a direct numerical simulation data set of active thermal Couette flows for different friction Richardson numbers, at the Prandtl number of air. The existence of these structures is linked to the nonexistence of an active thermal flow. As soon as the Richardson number is greater than 1.5, the structures are less energetic, and for a value of only 3, the structures have vanished. This is due to the reorganization of the intense Reynolds stress events. Thus, large-scale structures will hardly appear in real-life Couette flows of air with a stable wall-normal gradient of temperature.