Turbulent dispersion of particles in a differentially heated vertical channel

Abstract

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.

Direct numerical simulations of particle dispersion in the turbulent natural convection flow between two vertical walls kept at constant but different temperatures are reported. It is assumed that the particles do not affect the flow (i.e. the dilute phase approximation is adopted). Particles with different levels of inertia or Stokes numbers (0.843≤St≤17.45) are tracked according to the drag force imposed by the fluid. The gravity force is also included for two cases, St=0.843 and St=17.45. The different level of turbulence near the wall and near the center of the channel produces, as in isothermal turbulent channel or pipe flow, a larger concentration of particles near the wall. This effect becomes more important, and the deposition velocity of particles on the wall increases, as the particle inertia is increased in a certain range of Stokes numbers (0.843≤St≤8.38). The simulations at St=8.38 and St=17.45 predict similar concentration profiles and deposition velocities according to the large inertia of these particles. For the conditions considered, the gravity vector imposes a strong descending motion on particles and this produces the increase of the particle concentration near the wall in comparison with the results without the gravity force.