The roles of surface temperature and roughness in droplet splashing

Abstract

In this work, the effects of surface temperature and surface roughness on the splashing phenomena of droplet impact are experimentally investigated. The transition temperature, TTr, from the deposition regime to the rebound regime is determined on various rough surfaces. It is found that TTr decreases with increasing surface roughness. Furthermore, the critical splash number, Kc, above which droplet splash takes place, exhibits distinct dependences on the surface temperature when the surface temperature is increased across the transition temperature. Below TTr, Kc increases as the surface temperature is raised, and the increasing rate decreases as the surface roughness is increased. Above TTr, however, Kc decreases abruptly and becomes insensitive to both surface roughness and temperature. Theoretical analysis is carried out to elucidate the observations. The results in this work provide useful information for diverse industrial processes involving droplet splashing phenomena.