Dynamical demixing of a binary mixture under sedimentation

TL;DR

This paper studies how a binary mixture separates during sedimentation, revealing a threshold in velocity difference that causes segregation, supported by simulations and an analytical model.

Contribution

It introduces a combined simulation and analytical approach to understand the threshold-driven segregation in sedimenting binary mixtures.

Findings

Segregation occurs above a specific velocity difference threshold.

Degree of segregation increases with velocity difference.

Hydrodynamic effects influence the sedimentation morphology.

Abstract

We investigate the sedimentation dynamics of a binary mixture, the species of which differ by their Stokes coefficients but are identical otherwise. We analyze the sedimentation dynamics and the morphology of the final deposits using Brownian dynamics simulations for mixtures with a range of sedimentation velocities of both species. In addition, we use the lattice Boltzmann method to study hydrodynamic effects. We found a threshold in the difference of the sedimentation velocities above which the species in the final deposit are segregated. The degree of segregation increases with the difference in the Stokes coefficients or the sedimentation velocities above the threshold. We propose a simple analytical model that captures the main features of the simulated deposits.