Experimental and numerical investigation of drop evaporation depending on the shape of the liquid/gas interface

Abstract

We present experimental and numerical lifetime investigations of evaporating water drops on solid surfaces depending on the shape and size of their liquid/gas interface. The simulations are based on an Allen–Cahn type phase-field model, where the liquid–gas phase transition is driven by a concentration gradient. The experiments are conducted under defined initial and constant conditions. Throughout the whole experiment, contact angle, temperature, relative air humidity and drop weight are tracked continuously. The numerical and experimental results are compared with analytical predictions. In our study, we confirm that the lifetime of a drop is directly linked to its surface size and shape. We compare lifetimes of evaporating drops on smooth solid surfaces with different contact angles and find an increase in lifetime by 50% as the contact angle increases from 20° to 90°, both in experiments and in simulations. Furthermore, drops placed in different geometric set-ups such as a wedge or a corner show a lifetime behavior that is in accordance with analytical predictions. The presented computational approach captures experimentally measured drop lifetimes, for various set-ups, very well. These findings are especially relevant for industrial questions such as how fast complex components dry after cleaning or how long it takes till lacquer layers are cured on structured surfaces.