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.