Propagation and interaction of gravity currents resulting from successive release of two lock fluids*

Gravity currents are ubiquitous in the natural environment. This study investigates the interaction of gravity currents generated by successive releases of two lock-fluids using highly resolved numerical simulations. We examined three distinct scenarios: (a) simultaneous release of two lock fluids, (b) sequential release of two lock fluids, and (c) the release of a single lock fluid with a density equal to the average of the two lock fluids. Results show that mixing is significantly enhanced in the case of sequential release of lock fluids. Specifically, as the denser (trailing) current catches up with the lighter (leading) current, enhanced mixing of fluids is observed. This is mainly due to complex interaction that ensues leading to elevated shear at the head of the combined currents resulting in Kelvin-Helmholtz like instabilities. Analysis of the interaction between two currents is done as a function of the time of release (T_R), the time to catch (T_C) of the lighter current, and the ratios of the density of the lock fluids to the ambient fluid (ϒ₁, ϒ₂).