Convection in colloidal suspensions with particle-concentration-dependent viscosity

TL;DR

This paper investigates how particle-concentration-dependent viscosity influences the onset and nature of thermal convection in colloidal suspensions, revealing shifts in convection thresholds and flow patterns.

Contribution

It introduces a continuum model accounting for variable viscosity based on local particle concentration, analyzing its effects on convection thresholds and flow behavior.

Findings

Increased viscosity difference lowers convection threshold.

Convection onset shifts position depending on the separation ratio.

Both stationary and oscillatory convection are affected by viscosity variations.

Abstract

The onset of thermal convection in a horizontal layer of a colloidal suspension is investigated in terms of a continuum model for binary-fluid mixtures where the viscosity depends on the local concentration of colloidal particles. With an increasing difference between the viscosity at the warmer and the colder boundary the threshold of convection is reduced in the range of positive values of the separation ratio psi with the onset of stationary convection as well as in the range of negative values of psi with an oscillatory Hopf bifurcation. Additionally the convection rolls are shifted downwards with respect to the center of the horizontal layer for stationary convection (psi>0) and upwards for the Hopf bifurcation (psi<0).