SPH simulation of supercooled large droplets impacting hydrophobic and superhydrophobic surfaces

Abstract

Hydrophobic and superhydrophobic coatings are of great interest to the aerospace community as a measure to mitigate performance losses due to ice formation in flight. To numerically investigate the supercooled large droplets (SLDs) impacting such coated surfaces, a multiphase smoothed particle hydrodynamics (SPH) solver is developed by solving the Euler momentum equations for fluid dynamics, the energy equation for heat transfer and a latent heat model for phase changes. A continuum surface tension term is included in the momentum equations and a robust contact angle model that corrects the surface tension near triple-phase points is proposed to calculate the non-wetting effects of surfaces. The present solver is capable of modeling droplets impacting, spreading, retracting on and/or rebounding from hydrophobic/superhydrophobic surfaces, with heat transfer and phase change. It is first validated against the evolution of droplets on solid surfaces of various contact angles and then applied to droplets impacting hydrophobic and superhydrophobic surfaces at different temperatures. This work investigates SLD impingement and solidification on hydrophobic and superhydrophobic coatings and provides a base for the numerical experimentation of a single SLD icing behavior at in-flight speeds.