Influence of Sedimentation on Convective Instabilities in Colloidal Suspensions

TL;DR

This paper theoretically examines how sedimentation influences convective instabilities in colloidal suspensions under a vertical temperature gradient, revealing different bifurcation behaviors and hysteresis effects.

Contribution

It introduces a theoretical analysis of sedimentation effects on bifurcation scenarios in colloidal suspensions, highlighting the impact of sedimentation and Soret effect on instability behavior.

Findings

Different linear instability behaviors depending on sedimentation and Soret effect.

Existence of hysteresis between quiescent and convective states.

Coexistence of stationary states above a certain barometric number.

Abstract

We investigate theoretically the bifurcation scenario for colloidal suspensions subject to a vertical temperature gradient taking into account the effect of sedimentation. In contrast to molecular binary mixtures, here the thermal relaxation time is much shorter than that for concentration fluctuations. This allows for differently prepared ground states, where a concentration profile due to sedimentation and/or the Soret effect has been established or not. This gives rise to different linear instability behaviors, which are manifest in the temporal evolution into the final, generally stationary convective state. In a certain range above a rather high barometric number there is a coexistence between the quiescent state and the stationary convective one, allowing for a hysteretic scenario.