Numerical Study of the Superhydrophobic Nature of Triply Periodic Minimal Surfaces (TPMS): Energy Characteristics of Droplet Impact, Spreading and Rebounding Phenomena

Abstract

The impact and rebound dynamics of water droplets on surfaces featuring triply periodic minimal surfaces (TPMS) are examined, investigated, and compared against flat and solid substrates in this numerical study. Water droplets’ collision, spreading, retraction and ability to jump off from TPMS surfaces are evaluated using kinetic energy analysis. Two types of geometry, cuboid and cylindrical, in the form of four distinct types of triply periodic minimal surfaces are generated as porous substrates to study their ability for water repellency. At high contact angles, the droplets’ kinetic energy profiles are found to be considerably higher than the flat substrates, at low impact velocity/Weber numbers. At smaller contact angles, the difference between the kinetic energy profiles is considerably higher for TPMS surfaces compared to flat substrates. Thus, droplets on periodic porous substrates are able to jump off such surfaces while failing to detach from a purely flat surface. At the same time, higher speed impacts at the smaller contact angles result in droplets failure to jump off on certain TPMS substrates, and could be attributed to excessive impalement characteristics that are not present with the other three types of substrates. For the cylindrical substrates, a similar observation has been made, where at lower contact angles, the droplets fail to jump off the solid substrate but repellency occurs on the TPMS substrates. The variation of the radial ratios of the substrates is also presented to elucidate the different characteristics of TPMS substrates at the end of the study.