Effect of inertia on the dynamic contact angle in oscillating menisci

TL;DR

This study investigates how inertia influences the dynamic contact angle during oscillating menisci, revealing limitations of traditional models and proposing a new model that accounts for acceleration effects.

Contribution

The paper introduces a new model that incorporates inertia to better predict contact angles in accelerating conditions, especially for perfect wetting fluids.

Findings

Traditional models fail at high accelerations

Inertia significantly affects the contact angle

The new model improves prediction accuracy

Abstract

The contact angle between a gas-liquid interface and a solid surface is a function of the dynamic conditions of the contact line. Classic steady correlations link the contact angle to the contact line velocity. However, it is not clear whether they hold in presence of inertia and in the case of perfect wetting fluids. We analyze the shape of a liquid interface and the corresponding contact angle in accelerating conditions for two different fluids, i.e. HFE7200 (perfect wetting) and demineralized water. The set-up consists of a U-shaped quasi-capillary tube in which the liquid column oscillates in response to a pressure step on one of the two sides. We obtained the evolution of the interface shape from high-speed back-light visualization, and we fit interface models to the experimental data to estimate the contributions of all the governing forces and the contact angle. Traditional interface models fail to predict the interface shape and its contact angle at large interface and contact line accelerations. We propose a new model to account for the acceleration, and we discuss its impact on the measurement of the transient contact angle.