Coalescence-induced jumping of unequal-sized droplets on superhydrophobic surfaces

Abstract

In this study, a numerical investigation is conducted to explore the jumping behavior triggered by the coalescence of two droplets of different sizes on a superhydrophobic surface for a deep understanding of the jumping behavior and physical mechanisms, which can contribute to improving the performance of superhydrophobic surfaces for various applications relevant to the manipulation of droplet behavior. The results show that the upward centroidal velocity at a contact angle of 180° is 14.2% smaller than that at 169° at the jump-off moment. However, it is about 45.8% larger as the radius of the small droplet decreases from 200 to 50 µm. The jump-off occurs when the centroidal height is higher than the radius of the sphere estimated from the summed volumes of two coalesced droplets and when the coalesced droplet is with an upward velocity.