Hybrid atomistic-continuum simulation of nucleate boiling with domain re-decomposition method

Abstract

The bubble nucleation plays a pivotal role in the boiling process. In order to have a comprehensive understanding of this phenomenon, a critical consideration on fluid-solid interaction at atomistic level is imperative. However, traditional Molecular Dynamics simulation requires prohibited amount of computational efforts to accomplish a full scale study. Hybrid atomistic-continuum method is a promising solution for this problem. It limits the atomistic region to a small scale where detailed information is preferable, while using continuum method for the rest of the domain. Nevertheless, none of the current hybrid method is suitable for solving a rapid expanding system like the bubble nucleation. In this study, a domain re-decomposition hybrid atomistic-continuum method is developed to conduct a multiscale/multiphase investigation on the bubble nucleation. In addition to the conventional coupling scheme, this method is capable to re-partition the molecular and continuum domain once it is necessary during the simulation. That is, the Computational Fluid Dynamics (CFD) and Molecular Dynamics (MD) regions are interchangeable on the fly such that the bubble is absolutely confined within MD region. Giving the fact that accurate modeling of interface tracking and phase change are still problematic for continuum mechanics on microscale, our coupling method directly avoids these issues since CFD domain takes care of a single-phase flow while the molecular domain simulates the bubble growth. With this idea in mind, this approach enables us to investigate the nucleate boiling on nanostructured surface with higher resolution than complete continuum mechanic model based simulation. In the present result, it is observed that bubble grows at a curved surface imposed with a constant super heat after nucleate boiling occurs. Meanwhile, the energy flux flows from solid to fluid is measured during the entire process. It is believed that this coupling method is very promising in studying nano-bubble related multiphase problems on microscale.