Gravity currents under oscillatory forcing*

We investigate the evolution of two-dimensional gravity currents, resulting from the well-known lock-exchange set-up, when they are affected by an external oscillatory forcing introduced by superimposing a horizontally uniform oscillating pressure gradient. We explore the effect of the velocity amplitude of the applied oscillating flow and its period of oscillations on the behavior of the evolving gravity currents. A key element introduced by the external forcing is the Stokes boundary layer near the no-slip bottom wall generating differential advection resulting in lifting of the gravity current. We have explored the effect of lifting on current propagation and the density structure of the current front. Our study shows the existence of significant effects of an oscillatory forcing on the dynamics, advection, and mixing properties of gravity currents.