Flow reversals in particle-dispersed natural convection in a two-dimensional enclosed square domain

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Abstract

Shintaro Takeuchi, Yuri Miyamori, Jingchen Gu, and Takeo Kajishima, "Flow reversals in particle-dispersed natural convection in a two-dimensional enclosed square domain," Physical Review Fluids, 4, 084304, 2019. https://doi.org/10.1103/PhysRevFluids.4.084304.

Flow reversals in natural convection of particle-dispersed two-phase flow in a two-dimensional square box are studied by numerical simulation. The Rayleigh number based on the domain side length is set to 10^4. The domain accommodates 11^2 neutrally buoyant circular particles, and the thermal conductivity of the particle is set to 10^2 times higher than the ambient fluid. The particle-dispersed flow driven by buoyancy develops into circulating flow, which transports particles into a diagonal pair of corner regions of the domain. The particles vertically aligned in the corner regions are a strong source of moment of buoyancy in the counterconvective direction, and flow reversals take place at the intervals of several hundred convective-time scales. The mechanism is different from that of the reversals or oscillation in single-phase or particle-dispersed natural convection reported in the literature. Thermal effect of the vertically aligned particles in a corner is modeled by nondimensionalized heat flux, and a cross-coupled sum of those of the four corners is found to be a precursor indicator of the reversal events. The investigation on the effects of three major parameters (Rayleigh number, conductivity ratio, and average interparticle spacing) suggests that the reversals occur in a small region in the parameter space.

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