Simulation of Solid Particles Behavior in a Heated Cavity at High Rayleigh Numbers

Transport and deposition of solid particles in a differentially heated cavity at high Rayleigh numbers up to 10(8) was studied using an Eulerian-Lagrangian computational method. Two-dimensional Navier-Stokes and energy equations were solved and the motions of particles with diameters in the range of 10 nm to 10 mu m were simulated. Effects of drag, lift, thermophoresis and Brownian forces on the particle trajectories were investigated. It was observed that the variation of Rayleigh number can significantly change the flow field and the corresponding particle deposition patterns. In particular, recirculation regions were formed near the corners as the Rayleigh number increased. Furthermore, the effects of changes in the Rayleigh numbers on transport and deposition of particles of different sizes were quite different. Increasing Rayleigh number from 10(7) to 10(8) caused a decrease in particles deposition except for 10 mu m particles. Smaller particles had a higher probability to deposit on the cold wall as the thermophoresis effect becomes important. Increasing the Rayleigh number decreased the influencing zone of the thermophoresis in the vicinity of the walls.