A conservative pressure based solver with collocated variables on unstructured grids for two-fluid flows with phase change

Numerical simulation of two-phase flows based on the two-fluid six-equation model is the focus of this work. This approach is widely used in thermo-hydraulics for many industrial applications, particularly nuclear power plant safety analysis. A semi-implicit numerical method that has been successfully adopted in several industrial thermo-hydraulic codes, because of its efficiency and robustness, has been extended. In this paper, the governing equations are solved on unstructured grids with collocated variables to accommodate complicated geometries, and a deferred-correction method is used to deal with the non-orthogonality of unstructured grids. In addition, the numerical method is conservative, meaning that it is capable of capturing a shock wave exactly in single-phase flows, and ensuring the conservation of physically conservative quantities of a two-phase flow mixture. Numerical benchmarks and industrial test cases are performed in order to validate the numerical method and to evaluate its behavior with respect to different physical configurations. •The two-fluid six-equation model was used to simulate two-phase flows.•A semi-implicit method was extended to unstructured grids with collocated variables.•A conservative scheme, that ensures the exact conservation of mass, momentum and total energy of a mixture, was developed.•Numerical benchmarks and industrial test cases were performed using a tabulated EOS.