Horizontal oscillation of a capillary bridge between a spherical grain and a flat surface

Instituto de Física Aplicada, CONICET, Universidad Nacional de San Luis, Ejército de los Andes 950, 5700 San Luis, Argentina

Published online: 1 December 2025

Abstract

A granular system's behaviour can be significantly altered by humidity, as even small amounts of condensed liquid between grains affect particle movement. Capillary bridges form between grains, creating cohesive forces that hold particles together, particularly in the pendular state at low saturation. When shearing is applied to granular packing, these bridges deform, with their force depending on their shape, fluid properties, and particle velocity. This makes studying the deformation of liquid bridges crucial for modelling wet granular materials. This study examines the dynamic behaviour of a capillary bridge between a flat surface and a spherical particle using ethylene glycol as the liquid. The deformation is induced by oscillating the horizontal surface while keeping the sphere fixed, causing the meniscus geometry to change. High-speed video captures the deformation, allowing the measurement of advancing and receding contact angles. The angles' behaviour is analysed as a function of the capillary number for a given amplitude and frequency. The research seeks to identify differences in receding and advancing angles, supporting predictions from theoretical models about torsional motion on a liquid film. The limitations of these models are discussed.