Edge Wetting: Steady State of Rivulets in Wedges

TL;DR

This paper investigates steady-state rivulets in wedge-shaped channels, showing that surface forces can enable rivulets to violate classical capillarity conditions, with models accounting for wall deformability.

Contribution

It introduces a disjoining pressure-based model for rivulet formation in wedges, including effects of soft, deformable walls, challenging classical capillarity theory.

Findings

Steady rivulets can form in wedges despite Concus-Finn condition violations.

Surface forces enable stable rivulet configurations in wedge geometries.

Wall deformability influences rivulet shape and stability.

Abstract

The geometry of rough, textured, fractured and porous media is topologically complicated. Those media are commonly represented by bundles of capillary tubes when modeled. However, angle-containing geometries can serve as a more realistic portrayal of their inner structure. A basic element abidingly inherent to all of them is an open wedge-like channel. The classical theory of capillarity ignoring intermolecular interactions implies that liquid entering the wedge must propagate indefinitely along its spine when the liquid-gas interface is concave. The latter is well-known as a Concus-Finn condition. In the present paper, we show that steady-state rivulets violating Concus-Finn condition can be formed in such channels when the surface forces are taken into account. We present a simple model based on the disjoining pressure approach and analyze the shape of the rivulets in the wedges. Besides, we consider a case when the walls of the wedge are soft and can be deformed by the liquid.