Particle Re-Suspension in Two-Phase Dispersed Rayleigh-B\'{e}nard Convection

TL;DR

This study uses particle-resolved simulations to investigate how particles are re-suspended and transported in Rayleigh-Bénard convection, revealing the formation of dunes that influence particle entrainment into plumes.

Contribution

It introduces a detailed simulation approach to analyze particle re-suspension mechanisms in convection, highlighting the role of dunes in particle entrainment, which was previously observed but not thoroughly modeled.

Findings

Particles form dunes at the base of ascending plumes.

Dunes deflect flow and facilitate particle entrainment.

Re-suspension efficiency depends on fluid energy and dune dynamics.

Abstract

The process by which particles are entrained by the fluid in Rayleigh-B\'{e}nard convection is studied by means of particle-resolved numerical simulations in a periodic domain at a Rayleigh number of $10^7$. The fluid Prandtl number is 1 and the particle-to-fluid density ratio 1.1. The results show that the horizontal velocity field near the bottom of the cell accumulates particles in heaps, or `dunes', at the base of ascending plumes. The dunes deflect the incoming flow, conferring to it a vertical velocity component which entrains the particles up the dune and into the plume. An experimental observation of this mechanism was briefly reported by Solomatov et al. (Earth Planet. Sc. Lett. 120, 387, 1993) but has not been considered further in the literature. By its very nature, such a process cannot be simulated by the point particle model. The final particle load carried by the convection depends both on the available gravitational energy of the fluid and on the effectiveness of the re-suspension mechanism.