Collective Dynamics of Settling Particles in Turbulence – CoDSPiT

The dynamics of solid particles suspended in a fluid are a complex and fascinating problem of fluid mechanics, with applications in fields as diverse as environmental fluid mechanics, the petroleum industry, and chemical engineering industries. Among the various types of flows that occur in nature and industrial applications, sedimentation plays a central and fundamental role: it is indeed one of the simplest particulate flows one can think of, and yet encompasses many of the complex features that will arise in other settings. While most previous studies (both experimental and computational) of sedimentation have focused on the case of low-Reynolds-number flows, in which fluid and particle inertia can be neglected with respect to viscous forces, most practical applications of sedimentation actually involve inertia and/or turbulence.
The objective of the present study is to understand the effect of flow turbulence on particle settling rate. This effect is intimately related to the interactions of particles with local spatial structures of the flow, e.g. large vortices. These vortical structures have a significant effect on the local particle transport and concentration. Collective effect between the particles may also affect this settling. This latter effect has not been considered in previous studies and is at the centre of the present project.
We propose a jointed experimental and numerical study to examine these issues. The approach that we intend to follow is twofold. First, we would like to examine a 2D model experiment coupled with numerical simulations, which will provide physical insights of the physical mechanisms involved. Second, we will tackle real 3D turbulence using two situations: a fluidized bed and a sedimentation channel with an active grid. The numerical simulations validated in the 2D situations will be tested in this more complex 3D geometry.