Direct Numerical Simulation of the Sedimentation
of Solid Particles
with Thermal Convection
G. Gan, H., Chang, J., Feng, J. J. & Hu, H. H.
J. Fluid Mech. 481, 385-411 (2003)
Abstract - Dispersed two-phase flows often involve
interfacial activities such as chemical reaction and phase change, which
couple the fluid dynamics with heat and mass transfer. As a step toward
understanding such problems, we numerically simulate the sedimentation
of solid bodies in a Newtonian fluid with convection heat transfer. The
two-dimensional Navier--Stokes and energy equations are solved at moderate
Reynolds numbers by a finite-element method, and the motion of solid particles
is tracked using an arbitrary Lagrangian-Eulerian scheme. Results show
that thermal convection may fundamentally change the way that particles
move and interact. For a single particle settling in a channel, various
Grashof-number regimes are identified, where the particle may settle straight
down or migrate toward a wall or oscillate laterally. A pair of particles
tend to separate if they are colder than the fluid and aggregate if they
are hotter. These effects are analyzed in terms of the competition between
the thermal convection and the external flow relative to the particle.
The mechanisms thus revealed have interesting implications for the formation
of microstructures in interfacially active two-phase flows.