Author(s): Seng Keat Ooi; George Constantinescu; Larry Weber
Keywords: No Keywords
Abstract: The structure of intrusive Boussinesq gravity currents propagating into a two-layer fluid with a sharp interface are investigated using highly-resolved Large Eddy Simulation (LES). The intrusion current (IC) is created by the instantaneous release a finite volume of lock fluid whose density is between the densities of the two layers of ambient fluid. Two cases are studied corresponding to two of the experiments with saline fluid discussed in Sutherland et al. (2004). In the first one (SC), the depths of the two layers of ambient fluid are equal. In the second one (NSC), the depths of the two layers are different. In both cases, the density of the lock fluid is equal to the depth-weighted mean of the densities inside the two layers of ambient fluid. After an initial acceleration phase, the IC is found to travel at a constant speed in both simulations. The propagation speed is found to be close to experiments and theory. The vortical structure of the flow, the vertical and streamwise distributions of the local dissipation rate integrated over horizontal and, respectively, vertical planes are analyzed at different stages of the evolution of the ICs. Though most of the total dissipation is observed to occur in the dissipative wake region, the levels of the integral of the local dissipation rate at streamwise locations situated inside the head region are found to be comparable to those inside the wake region. This is due to the dissipation taking place in the thin shear layers at the front of the intrusion interface.