Flow modulation and heat transport of radiatively heated particles settling in Rayleigh–Bénard convection

We investigate the effect of radiatively heated solid particles settling in Rayleigh–Bénard turbulent flow. Three-dimensional fluid flow computations were performed using direct numerical simulation, while the evolution of particle temperature, velocities, and positions are obtained by Lagrangian particle tracking. We consider particles whose diameters vary form 20 µm to 80 µm subject to thermal radiation and settle in Rayleigh–Bénard cell at Rayleigh number Ra=2×10⁶. The results show that the sedimentation behaviors of the particles with different particle sizes are significantly different, and the trajectories of small particles are very chaotic compared to those of large particles. Consequently, small particles can absorb solar energy efficiently and result in gas temperature increase. As the particle size decreases, the thickness of the upper boundary layer becomes thinner, while the thickness of the lower boundary layer becomes thicker. The Nusselt number varies monotonically with a logarithmic function with the diameter of the particle on both the upper and lower walls.