Water Tank Simulation of a Dense Fluid Release

The turbulent velocity field of a dense fluid release has been measured in a water tank experiment carried out in the TURLAB laboratory in Turin (Italy). A vertical density driven current was created releasing a saline solution in a water tank with no mean flow. The experiment reproduces in physical similarity, based on the density Froud number, the release of a dense gas in the atmosphere and the PIV technique has been used to analyse the buoyancy generated velocity field. The high temporal and spatial resolution of the measurements gives a deep insight to the problems of the bouncing of dense gases and of the creation of the outflow velocity at the ground. The experimental findings are used to test and improve an original method for the dispersion of a positively and negatively buoyant plume. The method is based on the idea of Alessandrini and Ferrero (Phys. A 388:1375–1387, 2009) for the treatment of a background substance entrainment into the plume and it consists on the introduction of two fictitious scalars inside the Lagrangian Model SPRAY. The fictitious scalars represent the density and momentum difference between the plume and the environment air that naturally takes into account the interaction between the plume and the environment. As a consequence, no more particles than those inside the plume are released to simulate the entrainment of the background air temperature. In this way the entrainment is properly simulated and the plume sink is calculated from the local property of the flow. The approach is wholly Lagrangian.