Fog Harps: Elastocapillarity, Droplet Dynamics, and Optimization

Abstract

Fog harvesting is emerging as a promising means to ease the water shortage crisis in arid regions of the world with ample fog. The current state-of-the-art for fog harvesting is mesh netting, which is accessible yet struggles from a dual constraint: a course mesh lets most microscopic fog droplets pass through it, while a fine mesh clogs. In recent years, fog harps have been gaining attention as a superior alternative to meshes, bypassing these inherent constraints. In this work, we expand upon previous fog harp research with a focus on optimization. First, we analyze wire tangling in a harp due to capillary forces, resulting in a mathematical model that is able to predict when wire tangling will occur. Second, we systematically vary three key parameters of a fog harp (wire material, center-to-center wire pitch, and wire length), arriving at an optimal combination. Finally, we develop a numerical model to describe the dynamics of a fog droplet sliding down a harp wire while coalescing with others littered along it. By applying all knowledge acquired through these studies, the next generation of fog harps will push the performance ceiling of practical fog harvesters higher than ever.