Gravity current propagating against constant and pulsating counter flows

The paper presents a study of the evolution of two-dimensional gravity currents, propagating against constant and pulsating counter flow. The effect of mean and oscillatory velocity amplitude on the gravity current evolution, the onset of interfacial shear instabilities such as Kelvin-Helmholtz billows, unstable near-bed density stratification, and the resulting density redistribution is addressed. Two non-hydrostatic processes, shear-driven Kelvin-Helmholtz billows and Rayleigh-Taylor-like overturning induced by differential advection, enhance vertical mixing and horizontal transport of dense fluid within the gravity current and are expected to affect salt intrusion in estuaries.