Three-dimensional gravity currents: laboratory experiments and numerical simulations

Three-dimensional gravity currents were studied by numerical and experimental simulations. Lock exchange experiments were carried out in a Perspex tank divided by a sliding bulkhead into two parts, one filled with salty water and the other with tap water. When the gate is removed, the heavier fluid collapses forming the gravity current. Three experiments were performed testing three values of the gate opening d. The tests were acquired from the top of the tank by a CCD camera and an image analysis technique was applied to detect the position of the current’s front in the horizontal plane. A single layer, 2D, shallow water model was used to perform numerical simulations. The mathematical model takes into account the variation of density due to the entrainment of fresh water into the gravity current. Results show a decrease of the current’s speed as the gate opening d diminishes. The comparison between numerical and experimental results shows that the adopted model is a valid tool in reproducing gravity current’s dynamics.