Eur. Phys. J. E (2018) 41: 140
https://doi.org/10.1140/epje/i2018-11748-x

Regular Article

A note on evolution of pressure and flow within an evaporating capillary bridge

¹ Duke University, Mechanical Engineering and Materials Science Dept., Durham, NC, USA
² Laboratoire de Mécanique et Génie Civil (Université de Montpellier-CNRS), Montpellier, France
³ LMGC (Université de Montpellier-CNRS) & MIST Laboratory (IRSN-CNRS-Université de Montpellier), Montpellier, France
⁴ Duke University, Civil and Environmental Engineering Dept., Durham, NC, USA

^* e-mail: yangshu0813@foxmail.com

Received: 6 June 2018
Accepted: 30 October 2018
Published online: 5 December 2018

Abstract

Experiments with evaporation of capillary bridges between two glass spheres show that the bridge gorge radius decreases much faster than the contact radius, distorting the original constant mean curvature bridge shape. In addition, the Laplace pressure calculated from local principal curvatures exhibits high gradients along the bridge moving external surface, most commonly with a high suction near the triple phase contact and positive pressure near the gorge. The high suction results from a negative external curvature at contact. Numerical dynamic simulations with a moving evaporating interface do not currently allow for reproducing a negative external curvature at contact. A series of static simulations are shown based on a representation of an experimentally observed interface, which does include the negative curvature at contact. The resulting Laplace pressure distribution is close to the experimental ones. Most importantly, the pressure gradients induce a consistent flow of liquid from the central area of the bridge, axially toward the solid contact, and then along the solid interface toward the contact area. The flow is believed to contribute to contact pinning. Pinning is viewed as one of the precursors of capillary bridge rupture.