A multiscale volume of fluid method with self-consistent boundary conditions derived from molecular dynamics

Abstract

Molecular dynamics (MD) and volume of fluid (VOF) are powerful methods for the simulation of dynamic wetting at the nanoscale and macroscale, respectively, but the massive computational cost of MD and the sensitivity and uncertainty of boundary conditions in VOF limit their applications to other scales. In this work, we propose a multiscale simulation strategy by enhancing VOF simulations using self-consistent boundary conditions derived from MD. Specifically, the boundary conditions include a particular slip model based on the molecular kinetic theory for the three-phase contact line to account for the interfacial molecular physics, the classical Navier slip model for the remaining part of the liquid-solid interface, and a new source term supplemented to the momentum equation in VOF to replace the convectional dynamic contact angle model. Each slip model has been calibrated by the MD simulations. The simulation results demonstrate that with these new boundary conditions, the enhanced VOF simulations can provide consistent predictions with full MD simulations for the dynamic wetting of nanodroplets on both smooth and pillared surfaces, and its performance is better than those with other VOF models, especially for the pinning-

Dynamics of droplet impacting on a cone

“…The accuracy and efficiency of the interFoam solver for the simulation of multiphase flows was evaluated approvingly by Deshpande et al, 51 and has been widely applied to the study of droplet dynamics. [52][53][54] Due to the rotational symmetry of the simulation, only a quarter of the computation domain of 6×6×8 mm 3 is simulated to save computation resources as in Fig. 2.…”

Nanoscale sheared droplet: volume-of-fluid, phase-field and no-slip molecular dynamics

“…2017; Liu et al. 2021) alleviate the need to understand the fundamental mechanisms near the moving contact line, and provide a way to couple MD and CFM directly. This is another alternative that should be considered for efficient simulations of multiphase systems.…”

“…A good recent classification of multiphase models can be found in work by Soligo, Roccon & Soldati (2021). It must be recognized that the hybrid models (Zhang et al 2017;Liu et al 2021) alleviate the need to understand the fundamental mechanisms near the moving contact line, and provide a way to couple MD and CFM directly. This is another alternative that should be considered for efficient simulations of multiphase systems.…”

Molecular Dynamics Simulation on the Wettability of Nanoscale Wrinkles: High Water Adhesion of Rose Petals

“…Because nanoscale wrinkles are difficult to fabricate, experiments are challenging to access . Meanwhile, finite element simulations, which are commonly employed to research wetting properties, are also unable to quantitatively describe wetting phenomena at the nanoscale due to boundary effects . In recent years, some continuum theories − were adapted to analyze micro- and nanostructures’ wetting behavior and water adhesion.…”

“…28 Meanwhile, finite element simulations, which are commonly employed to research wetting properties, are also unable to quantitatively describe wetting phenomena at the nanoscale due to boundary effects. 29 In recent years, some continuum theories 30−32 were adapted to analyze micro-and nanostructures' wetting behavior and water adhesion. However, most models simplified the shape or dimension of structures.…”