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Proceedings of the 27th National and 5th International ISHMT-ASTFE Heat and Mass Transfer Conference December 14-17, 2023, IIT Patna, Patna-801106, Bihar, India
December, 14-17, 2023, Bihar, India

Particle cloud patterns in Rayleigh-Benard convection

Get access (open in a dialog) DOI: 10.1615/IHMTC-2023.870
pages 535-540


We study the settling of small but heavy particles in a rectangular two-dimensional Rayleigh-Benard system at a fixed Rayleigh number Ra = 105 and Prandtl number Pr = 0.701. Considering one-way particle-fluid coupling, we define a length scale called particle boundary layer thickness δp. Particles which are initialised below δp, settle quickly under gravity and the remaining particles form quasi-static clouds. The rate of particle settling after the time scale t/τr ~ Ο(1) (t is time, τr is the particle residence time) is low. Numerical results show that the total fraction of particles that settle and δp increase monotonically with increase in the particle Stokes number Stp. However, the horizontal distance between the two adjacent particle clouds Δ and the size of each particle cloud reduce with an increase in the Stokes number. The number of particles that settle on the bottom surface with time deviates significantly from the expected exponential law and they settle at a substantially slow rate for small Stokes numbers.