Drop deformation with soluble surfactants in linear flows: role of adsorption-desorption

TL;DR

This paper develops a second-order theoretical model for drop deformation in shear flow considering surfactant adsorption-desorption kinetics, revealing effects on deformation and orientation that differ from classical limits.

Contribution

It introduces new expressions for deformation and angle deviation incorporating surfactant kinetics, advancing understanding of surfactant effects on drop behavior in flow.

Findings

Surfactant adsorption kinetics influence drop deformation and orientation.

The model predicts less deformation than classical limits.

Minor corrections to the deviation angle are identified.

Abstract

Drop deformation in shear flow is determined up to second order theory in Ca while considering kinetic effects on surfactants distributions in steady state. Surfactants inside the drop are adsorbed faster than those on the surface leading to an increase in total surfactants concentration on the semi-minor axis of the ellipsoidal droplet. New expressions for Taylor deformation and angle deviation are proposed involving kinetics effects. Theoretical calculations lead to a possibility of lesser deformation than the usual limit condition and a minor correction for the deviation angle.