Liquid droplet morphology on the fiber of a fog harvester mesh and the droplet detachment conditions under gravity

TL;DR

This study investigates how liquid droplets form and detach on fibers in fog harvesting, using numerical simulations to understand the influence of gravity, fiber size, and wettability on droplet morphology and shedding conditions.

Contribution

It introduces a numerical approach to predict droplet shapes and detachment conditions on fibers considering various physical parameters, advancing the design of fog harvesting systems.

Findings

Droplet morphology varies between 'barrel' and 'clamshell' shapes depending on parameters.

A relation between shedding volume and Bond number is established.

Detachment volumes are quantitatively calculated based on the model.

Abstract

Liquid droplets on fiber are often observed both in nature and in different engineering applications, like a fog harvesting mesh. Knowledge about drop-on-fiber morphology and its shedding under the influence of gravity can allow for the design of better separation technology. Mutual interaction of surface tension forces arising out of the surface energies of the liquid and the fiber solid, and the weight of the liquid droplet gives rise to different morphologies of the droplet, which may occur in a stable or meta-stable configuration. Predicting the droplet shape on a fiber of specified dimension and surface wettability accurately for a given volume of liquid is challenging since the curvature of both the droplet and the cylinder influence the phenomenon. We have numerically investigated the droplet shape and transition criterion for various volumes at different contact angles under the effect of varying Bond numbers using an open-source surface evolver code. It is observed that depending upon the relative dimensions of the liquid droplet, the fiber diameter, wettability, and gravity, the liquid exists on the fiber either in 'barrel' or in 'clamshell' shape. A relation between shedding volume and the Bond number is deduced, and the detachment volumes are calculated.