Coalescence-induced droplet detachment on low-adhesion surfaces: A three-phase system study

: Coalescing water droplets on superhydrophobic surfaces can detach from the surface without the aid of any external forces. This self-propelled droplet detachment mechanism is useful in many applications, such as phase change heat transfer enhancement, self-cleaning surfaces, and anti-icing and antidew coatings. In this article, the coalescence-induced droplet jumping in a three-phase system is numerically investigated. The gaps between the surface structures are filled with a liquid that is immiscible with water, e.g., lubricant. A mass-conserving lattice Boltzmann method is implemented to study the effects of several parameters, such as interfacial tensions, droplet size, and surface wettability on the jumping process. The numerical results show that for relatively high values of lubricant-water interfacial tensions and large surface-water contact angles (>150^{∘}) the water droplets are capable of detaching. The critical droplet size for jumping is also highly dependent on the lubricant-water interfacial properties. The results of this study provide insights into the fluid-fluid and fluid-solid interactions and shed light on the underlying mechanisms involved in the droplet coalescence process on such surfaces.