A Theoretical and Numerical Study of Density Currents in Nonconstant Shear Flows

Abstract

The previous idealized two-fluid model of a density current in constant shear is extended to the case where the inflow shear is confined to the low levels. The analytical solution is determined by the conservation of mass, momentum, vorticity, and energy. It is found that a low-level shear acts in a similar manner to a uniform vertical shear in controlling the depth of a steady-state density current. When the shear enhances the low-level flow against the density current propagation, the current is deeper than half of the domain depth. Time-dependent numerical experiments are conducted for a variety of parameter settings, including various depths and strengths of the shear layer. The numerical results agree closely with the theoretical analyses.