Simulation of two-phase flow drift flux model in a vertical channel using Newton–Krylov method

In the present work, a numerical method is proposed in order to model the subcooled boiling flow in a vertical channel using the Drift Flux Model. The system of nonlinear equations is solved with the fully-implicit scheme using the Jacobian-free Newton–Krylov (JFNK) method. In order to improve the efficiency of the JFNK method and its numerical stability, a semi-implicit physics based preconditioning (PBP) is implemented. Recently, the JFNK method has been widely used to solve large and sparse system of equations. To validate the proposed method, the results were compared with the experimental data, the results of modeling by using the RELAP5 code, and the available numerical results in the literature. It was found that the results corresponding to the present work have a good agreement with those of the other mentioned methods. Also, it was found that the convergence rate of the JFNK method with the PBP is at least 50% higher than the JFNK method, and the void fraction mean absolute percentage error (MAPE) is less than 7.34% over a wide range of flow and pressure