The wetting problem of fluids on solid surfaces. Part 1: the dynamics of contact lines

TL;DR

This paper investigates the complex dynamics of contact lines where two fluids meet a solid surface, proposing a new model that accounts for non-Newtonian behavior and introduces a dynamic contact angle relation.

Contribution

It offers a novel perspective on wetting dynamics by revisiting the kinematics and equations of motion, including a new Young-Dupré equation for dynamic contact angles.

Findings

Velocity field is multivalued at the contact line.

Line friction concept is introduced with bounded stresses.

A new dynamic contact angle relation is proposed.

Abstract

The understanding of the spreading of liquids on solid surfaces is an important challenge for contemporary physics. Today, the motion of the contact line formed at the intersection of two immiscible fluids and a solid is still subject to dispute. In this paper, a new picture of the dynamics of wetting is offered through an example of non-Newtonian slow liquid movements. The kinematics of liquids at the contact line and equations of motion are revisited. Adherence conditions are required except at the contact line. Consequently, for each fluid, the velocity field is multivalued at the contact line and generates an equivalent concept of line friction but stresses and viscous dissipation remain bounded. A Young-Dupr\'e equation for the apparent dynamic contact angle between the interface and solid surface depending on the movements of the fluid near the contact line is proposed.