Particles deposition in gravity current by Lagrangian markers: Effect of topography and shear-induced lift force

A gravity current in a channel in the presence of obstacle with different heights, and a channel without obstacle, have been investigated by means of LES simulation and using Eulerian approach. The Saffman-Mei equation is used to investigate the effect of shear-induced lift force on the particles deposition. Toward this end, particles as Lagrangian markers have been injected into gravity current, it is important to keep in mind that interaction between gravity current and the particles has been treated as a one-way coupling. The results show that the shear-induced lift force is important in the locations with large velocity gradient such as entrance regions and near the obstacles. On the other hand, results show that the obstacle with the height of 2.58cm, not only causes the reduction in deposition by 18.26% at the downstream, but also reduces the deposition by 2.98% at the upstream. With increasing the height of obstacle, a reduction in amount of deposits can be seen in regions before and after the obstacle, in comparison with shorter obstacle. Blocking of flow by obstacle at the downstream, and turbulent structure of gravity current (caused by bore which is intensified by the height of obstacle) at the upstream, prevent the deposition of particles. Q criterion and bed shear stress are used to gain a better insight into depositional behavior, in different locations of channel.

Keywords:

Gravity current , Lift force , Particle deposition , Wall shear stress , Lagrangian markers