Characteristics of colliding density currents: A numerical and theoretical study

Abstract

This paper presents a new set of numerical simulations of two colliding density currents in a idealized framework, integrating the Boussinesq vorticity equation in a rectangular bounded domain. These simulations are used to examine the dynamical features of the collision, in the light of recent laboratory experiments. The collision dynamics present various interesting features. Here we have focused on the interface slope at the front of the two unequal density currents and on the maximum height reached by the fluid after the collision. For the secondary triggering of atmospheric convection by colliding cold pools from previous convective events, these may affect the positioning and the momentum of the collision uplift, respectively.The interface slope has been shown to be dependent on the currents' buoyancy ratio (i.e. the ratio between the density differences of the two fluids with the ambient fluid), whereas the maximum height has no strong dependence, for a given initial current depth. A theoretical model, based on an analogy with a vortex pair, has been proposed for the interface‐slope dependence, taking as input the buoyancy ratio or the propagating speeds. This model agrees reasonably well with the observed numerical values.