Droplet detachment from a horizontal fiber of a fog harvesting mesh

Fog capture holds promise in ameliorating the drastic freshwater crisis that is globally imminent. Metal meshes have shown promise in capturing both natural and industrial fogs, the latter primarily referring to cooling tower fog harvesting. However, there exists room for improvement of their water collection efficiency, which has been reported to be highly dependent on mesh wettability, geometry, and orientation with respect to the fog-laden wind. As fog droplets impinge and deposit on mesh fibers, they coalesce with previously deposited liquid to evolve as larger drops of different size and shape, depending on the mesh wettability and arrangement. While the primary intent of fog harvesting is to effectively drain the intercepted fog water along the mesh into a desired collector, premature drainage of the droplet is found to be detrimental to mesh performance. We investigate droplet detachment as a function of fiber diameter under real fogging scenarios. The results are compared with pre-existing droplet detachment theories and with numerical simulations using Surface Evolver. Droplet detachment volume is found to increase with the mesh-fiber diameter. It is also found that the existing theories of droplet detachment from fibers do not give reliable accuracy for detachment volume estimation under realistic fog-collection scenarios.