Entrainment in gravity currents over complex boundaries (C. Adduce, La Sapienza Roma))

Gravity currents are flows caused by a density difference between two fluids, which can be due to temperature and salinity gradients or sediment concentration. Gravity currents can occur in the oceans as dense currents and turbidity currents or in the atmosphere as avalanches and sand storms. These currents develop over complex boundaries and the interaction with the topography can deeply affect the dynamics of these flows, the associated mixing and modify the final proprieties of water masses. A simple technique employed to produce gravity currents in the laboratory is the lock-release. It consists in filling a tank with two fluids at different density separated by an impermeable sliding gate. When the gate is removed the two fluids interact and produce a dense current which propagates along the bottom of the tank and entrains ambient fluid.