Density Current Circulations in Shear Flows

Abstract

This paper develops an idealized (inviscid two fluid), two-dimensional, steady-state model of a density current circulation and its front propagating into a uniformly sheared environmental flow. This fully nonlinear analytical model is used to examine the kinematic and dynamic factors that control the depth and propagation speed of the density current and the geometric shape of the density current front. The results show that in comparison with the environmental inflow shear, the strength of the internal circulation within the cold pool of a density current plays a secondary role in controlling the depth and propagation speed of the density current, at least one having constant vorticity. The direction of the cold pool circulation can be either clockwise or anticlockwise, not affecting the propagation speed, depth, and geometric shape of an inviscid conservative density current. Physical interpretation of the results is provided in regard to the way that the inflow shear controls the shape of the density current head and produces the ?optimal state? for supporting long-lived squall lines.