Numerical study of droplet evaporation on heated flat and micro-pillared hydrophobic surfaces by using the lattice Boltzmann method

The evaporation processes of sessile droplets on both heated flat and structured hydrophobic surfaces are numerically studied by using a thermal multi-phase lattice Boltzmann model. The contact-line dynamics and heat transfer regarding the evaporation of droplets are simulated and the effects of the heat conductivity, wettability, and roughness of the substrate on the droplet evaporation are investigated. The results indicate that the different evaporation modes of the droplets on the rough surfaces are attributed to the microscopic "stick-slip" motion of the contact line. The constant contact angle (CCA) mode of droplet evaporation on the rough hydrophobic surface can be regarded as a macroscopic average of the microscopic "stick-slip" processes with a short stick period and small change in apparent contact angle. The weaker stick effect of the surface with a higher hydrophobicity and smaller solid fraction makes the droplet evaporation more likely to occur in the CCA manner. (c) 2020 Elsevier Ltd. All rights reserved.