Modeling the dynamics of partially wetting droplets on fibers

Abstract

We simulate gravity-driven dynamics of partially wetting droplets moving along a fiber using the lattice Boltzmann method. For the so-called clamshell morphology, we find three possible dynamic regimes upon varying the droplet Bond number and the fiber radius: compact droplet, droplet breakup, and droplet oscillation. For small Bond numbers, in the compact droplet regime, the droplet reaches a steady state and its velocity scales linearly with the driving body force. We find two scaling laws depending on whether the droplet size is smaller or larger compared to the fiber radius. In addition, we further identify a scaling law applicable for the barrel morphology. For higher Bond numbers, in the droplet breakup regime, satellite droplets are formed trailing the initial moving droplet. We find such droplet satellite formation is easier with increasing fiber curvature (smaller fiber radius). Finally, in the droplet oscillation regime, favored in the midrange of fiber radius, the droplet shape periodically extends and contracts along the fiber.

Wetting Effect Induced Depletion and Adsorption Layers: Diffuse Interface Perspective

“…While various models have already explored the depletion/ adsorption layer, [17] a diffuse interface model has not yet been employed to scrutinize its formation mechanism and thickness. Within the diffuse interface theory for wetting phenomena, prevalent models [23][24][25][26][27][28] assume identical composition on the surface and in the bulk of the fluids. The identical bulk and surface composition is achieved by utilizing the associated wall free energy and the bulk free energy with minima at the same composition.…”

Sliding, vibrating and swinging droplets on an oscillating fibre

“…(2010) studied this in detail for droplets that perfectly wet fibres while Christianto et al. (2022) recently investigated numerically the effect of a finite contact angle. In addition to these passive mechanisms, external perturbations in the form of standing waves (Bick et al.…”

“…Droplets on non-horizontal fibres slide when the gravitational force overcomes contact angle hysteresis. Gilet et al (2010) studied this in detail for droplets that perfectly wet fibres while Christianto et al (2022) recently investigated numerically the effect of a finite contact angle. In addition to these passive mechanisms, external perturbations in the form of standing waves (Bick et al 2015) or wind (Dawar et al 2006;Dawar & Chase 2008;Sahu et al 2013;Bintein et al 2019) also lead to directional transport.…”