A Hybrid Approach of Molecular Dynamics and S-Model Boltzmann Kinetic Equation Simulation for Evaporation Modelling

Accurate simulation of evaporation is vital for engineering applications, yet traditional methods face limitations. Molecular Dynamics (MD) offers high accuracy but is computationally intensive, while the S-model Boltzmann Kinetic Equation (SBKE) efficiently models rarefied gas flows but lacks a robust surface boundary condition. To overcome these challenges, we propose a novel hybrid MD-SBKE method for nano – and micro-scale evaporation. MD simulates the liquid phase and interface, while SBKE handles the vapour region, bridging microscopic and mesoscopic scales. This approach addresses the critical challenge of mass transfer between regimes during evaporation. Validated through numerical experiments, our one-dimensional hybrid model simulates argon nanoscale thin-film evaporation in parallel plate geometry. Results demonstrate improved accuracy over pure SBKE and significant computational efficiency gains compared to pure MD, enabling reliable evaporation modelling at reduced cost.