Numerical simulation of stratified intrusive gravity current in three-dimensional state due to the presence of particles using large eddy simulation method

Abstract

The motion of gravity current is attributed to the difference in density of current and the surrounding environment. If a fluid with a certain density enters the stratified environment so that its density is less than the lower layers and higher than the upper layers, the gravity current would be of intrusive type. Turbidity current is known as an important class of density currents, where the density difference is formed due to the presence of suspended solid particles in the fluid. In this paper, a three-dimensional numerical simulation of stratified intrusive gravity current in the presence of particles is investigated. For this purpose, the open-source OpenFOAM code is implemented for large eddy simulation to model the flow turbulence. According to the obtained results, the addition of particle mass to the intrusive gravity flow in dual symmetric state and flat bed would be followed by reduced velocities of intrusive gravity forward advance and ambient return flow at the bottom of the channel. Moreover, the flow behavior for the case of reverse slopes of 2, 4 and 6° in dual symmetric state in the absence of particles and at a 4° slope in the presence of particles with diameters of 20 and 30 microns has been investigated. Finally, the effect of bed slope on the instability of ambient gravity flow in the absence and presence of particles has explored with the help of local Richardson number. Faster instability in gravity current was achieved as a result of an increase in the bed slope in the absence of particles. Moreover, examining the instability in the 4° bed slope in the presence of particle with diameters of 20 and 30 microns revealed a reduction in local Richardson. Hence, the higher stability of the flow in the presence of particles compared to their absence can be inferred.