Quantitative measurements of the lift force acting on a sphere sliding along a liquid-liquid interface

TL;DR

This paper investigates the lift force on a sphere moving near a liquid-liquid interface, combining experiments and theory to understand how various factors influence the force and validating a soft lubrication model.

Contribution

It provides a systematic experimental validation of soft lubrication theory for lift forces on particles near liquid interfaces, considering multiple influencing factors.

Findings

Lift force increases as the particle approaches the interface.

Lift force saturates at short separation distances.

Experimental results agree with theoretical predictions.

Abstract

This work explores the lift force experienced by a particle moving in a viscous fluid near a liquid-liquid interface. The lift force is induced by the interaction between the viscous flow generated by the particle's motion and the deformation of the soft interface. The factors influencing the lift force including the velocity, the viscosity, and the sphere radius, and the separation distance were systematically studied. The experiments demonstrate that the lift force intensifies as the particle approaches the interface, and saturates at shorter distances. These findings are consistent with predictions made using soft lubrication theory and numerical calculations, providing strong validation for the theoretical framework.