Fluctuating interface in a dilute sedimenting suspension.

The evolution of large-scale fluctuations in a monodisperse dilute suspension sedimenting in a wall-bounded container is considered on the basis of a continuum model. The case when the velocity fluctuations are comparable with the Stokes settling velocity is studied. Small deformations of the sedimentation front is replaced by a flat interface with a surface force distribution. The front holds position ensuring the vertical fluid velocity across the front to be small. So it acts approximately as a no-slip wall. The mechanisms of the fluctuation decay are the convection of large-scale concentration disturbances and the sedimentation-front deformations.