Level Set Method Based Simulations on Impact-Dynamics of Bouncing and Non-bouncing Droplet on Super-Hydrophobic Substrates

Abstract

The present work investigates the spreading, receding and bouncing dynamics of a droplet falling on a superhydrophobic substrate. CMFD (computational multi-fluid dynamics) simulations are done using a DGLSM (dual grid level set method) based in-house code in an axisymmetric cylindrical coordinates. The available dynamic contact angle model from the literature is implemented in the code—to capture dynamic wetting of the droplet on the substrate. The deforming liquid-gas interface—during the droplet impact—is tracked using zero level set function. The droplet impact is modelled such that liquid vapor diffusion in the atmosphere, viscosity and surface tension variation with temperature are considered negligible. The droplet, substrate and surrounding air are at atmospheric conditions. Advancing and the receding contact angle of the droplet with the substrate (i.e. the wettability of substrate) are found to play a vital role in the modeling of impact dynamics of droplet. Numerically obtained temporal evolutions of the droplets are compared with published experimental results; for bouncing as well as non-bouncing droplets. Other than the instantaneous interface shape, the comparison is also done for temporal variation of droplet height and wetting diameter. The comparison is good—validating our DGLSM for the impact-dynamics.