Numerical study on heat and mass transfer of droplet collision on superheated bio-inspired surfaces

Abstract

The velocity and temperature fields of droplet evaporation on bio-inspired surfaces are investigated based on the single-component multiphase pseudopotential lattice Boltzmann method and liquid-vapor phase-change model. The morphology of the surface is inspired by the hierarchical cuticle of springtails which have the feature of doubly reentrant pillars. The dynamic mechanism of droplet collision and evaporation is revealed in the study. The effects of Jakob number, solid thermal conductivity, and pillar spacing on the behavior of the droplet collision on superheated bio-inspired surfaces are statistically analyzed. The study provides detailed snapshots depicting the evolution of droplet morphology. The trends of substrate heat flux, droplet lifetime, and droplet volume with time are presented. For the doubly re-entrant superheated surface, the droplet is easier to split and the droplet lifetime is shorter compared to that on smooth substrates. The reduction ratio of droplet lifetime is 66.2 % when Jakob number equals 0.12. When Jakob number increases, Leidenfrost vapor layer is generated on the surface and it deteriorates droplet evaporation. The lifetime of droplets does not consistently decrease with increasing solid-liquid thermal conductivity ratio across different Jakob numbers, primarily due to variations in droplet morphology under different conditions. Moreover, an increase in pillar spacing leads to an enhancement in the evaporation rate under the same superheating conditions. The droplet lifetime of 20 pillar spacing is 58.72 % of 8 pillar spacing.