Existent condition of partially wet state in capillary tubes

TL;DR

This paper develops a theoretical model to predict the equilibrium wetting states of fluids in cornered capillary tubes, identifying conditions for the existence of partially wet states.

Contribution

A new theory predicting equilibrium wetting states in cornered capillaries, including phase diagrams and conditions for partially wet states.

Findings

Partially wet states exist only within specific contact angle and corner curvature ranges.

The phase diagram delineates regions for dry, partially wet, and fully wet states.

The model applies to square tubes with rounded corners.

Abstract

We develop a theory that predicts the equilibrium states of a fluid contained in a capillary which has corners. Each section of the tube can take three states: completely wet state where the tube section is completely occupied by the fluid, partially wet state where only the corners are occupied by the fluid known as corner film or finger, and completely dry state. We calculate the phase diagram of these states for a square tube with rounded corners. It is shown that the partially wet state can exist only in a certain region in the parameter space spanned by the equilibrium contact angle and the corner curvature.