Deposition of a particle-laden film on the inner wall of a tube

TL;DR

This paper investigates how particles deposit on the inner wall of a capillary tube during liquid withdrawal, identifying key parameters affecting contamination and proposing conditions to prevent it or utilize it for coating.

Contribution

The study experimentally analyzes particle deposition during air invasion in capillary tubes and develops a model to optimize conditions for avoiding contamination or enabling coatings.

Findings

Particle deposition depends on particle-to-tube radius ratio and capillary number.

A model predicts conditions to prevent contamination during suspension withdrawal.

Deposition mechanisms can be used for controlled inner wall coatings.

Abstract

The withdrawal of a liquid or the translation of a liquid slug in a capillary tube leads to the deposition of a thin film on the inner wall. When particles or contaminants are present in the liquid, they deposit and contaminate the tube if the liquid film is sufficiently thick. In this article, we experimentally investigate the condition under which particles are deposited during the air invasion in a capillary tube initially filled with a dilute suspension. We show that the entrainment of particles in the film is controlled by the ratio of the particle and the tube radii and the capillary number associated with the front velocity. We also develop a model which suggests optimal operating conditions to avoid contamination during withdrawal of a suspension. This deposition mechanism can also be leveraged in coating processes by controlling the deposition of particles on the inner walls of channels.