Sedimentation of a surfactant-laden drop in a liquid with particles

TL;DR

This study uses 2D simulations to analyze how surfactants and particles affect the sedimentation behavior of a liquid drop, revealing complex interactions between surface tension, deformation, and flow dynamics.

Contribution

It introduces a simulation framework that models the combined effects of surfactants and particles on drop sedimentation, highlighting the impact of surface tension gradients and particle concentration.

Findings

Surfactants decrease surface tension and alter settling velocity.

Increased particle concentration leads to larger drop deformation.

Higher Peclet number reduces settling velocity due to surface tension gradients.

Abstract

This project aims to study the sedimentation of a surfactant-laden drop in a liquid with particles. A 2D simulation is performed with MATLAB. The interface is captured by the front-tracking method. The local viscosity depends on the local particle concentration, which follows a power law. The surfactants not only decrease the surface tension but also induce a surface tension gradient. If the surface tension decreases, the settling velocity will decrease due to a larger deformation of the drop (i.e., the drop becomes more flat). Additionally, increasing the Peclet number (ratio of convection to diffusion on the interface) for surfactants will reduce the settling velocity due to a larger surface tension gradient.