Modelling and simulation of surface-tension-dominant two-phase flows with an improved geometric volume of fluid framework

Two-phase flows with surface tension are ubiquitous in engineering applications. A high-fidelity numerical framework for capturing sharp interfaces and eliminating unphysical spurious currents is of great significance. To this end, an improved geometric VoF framework combining a numerical filtering approach to accurately calculate surface tension and effectively suppress spurious currents has been presented. Unlike traditional algebraic VoF approaches, our framework accurately captures sharp interfaces without any interface diffusion. Our improved numerical framework is implemented in the open-source C++ library OpenFOAM. Both two- and three-dimensional numerical benchmark cases are conducted to demonstrate the performance of our framework in suppressing spurious currents. Our framework shows the most superior performance when comparing against numerical results of two geometric VoF solvers, namely interIsoFoam and interFlow. Droplet spreading on a wall is employed to evaluate the performance of our framework in maintaining pre-specified contact angles on both hydrophilic and hydrophobic walls. Rayleigh-Taylor instability benchmark case shows the capability of our framework in capturing sharp interfaces for both cases with and without surface tension. Buoyancy- driven bubble rising simulations demonstrate improved accuracy in predicting bubble rising velocity without numerical oscillations. Furthermore, our model and numerical method are utilized to investigate the surface- tension-dominant droplet coalescence. Numerical results demonstrate the promising capability of our enhanced framework in predicting droplet spreading and coalescence dynamics.