Fully resolved particulate Rayleigh-Benard convection

Simplified models show that Rayleigh-Benard convection is relatively inefficient at maintaining particles in suspension (Solomatov & Stevenson, J. Geophys. Res. 98 5375 1993). In this work the behavior of heavy particles suspended in Rayleigh-Benard convection is investigated using particle-resolved simulations. The particle weight and the downward plumes cause a tendency for particles to deposit on the bottom wall. The key physical process to maintain a significant fraction of particles suspended is therefore the lifting of the deposited particles, a process that it is difficult to describe with a point-particle model. We focus on this aspect of the problem by means of the simulation of few particles in a slender domain with a square cross section in the vertical direction. The results show that the particle lift is primarily due to the plume generated by the particle itself. We also perform simulations in a cubic cell with up to 500 particles and 3.27% volume fraction finding that interaction with other particles increases the resuspension of deposited particles. As the total particle load increases (by increasing volume fraction or weight), a greater fraction of particles resides for a longer and longer time on the bottom of the domain.