Thermal effects on the sedimentation behavior of elliptical particles

Abstract

We investigate thermal effects on the sedimentation behavior of elliptical particles via particle-resolved direct numerical simulation. Two scenarios of fluid-particle heat transfer in an infinitely long channel are considered: one is a cold particle settling in a hot fluid, while the other is a hot particle settling in a cold fluid. Results show that when an elliptical particle sediment in a wide channel (i.e., the block ratio is large), in addition to the two sedimentation modes reported in the literature for the particle sediments in isothermal fluids, there exist another three modes arising from thermal effects: the tumbling mode, the anomalous rolling mode and the inclined mode. Specifically, for a cold particle settling in a hot fluid, we found the tumbling mode and inclined mode, while for a hot particle settling in a cold fluid, we found the anomalous rolling mode and inclined mode. The phase diagrams of the sedimentation modes as functions of Archimedes and Grashof numbers are given. Analyses of the relationship between particle Reynolds number and Grashof number indicates that the mode presented depends on the competition between channel wall confinement, combined forced and natural convection.