Transient analysis method for two-dimensional discharge flow using a two-fluid model

Recent advancements in reactor safety analysis require more detailed predictions of two-phase flow behavior. Therefore, a transient calculation method has been developed for two-dimensional two-phase flow using the two-fluid model. This method treats non-equilibrium two-phase flows by solving the partial differential equations of mass, momentum, and energy balances for each phase. With the finite difference method, which is widely used for two-phase flow analysis, difficulties are incurred when the finite difference of gas velocity is calculated between a node with two-phase mixture and one with single-phase water and no gas velocity. The present method employs the control volume formulation in order to avoid this difficulty and it is designed to simulate local two-dimensional two-phase flow dynamics. The objective of this paper is to outline the fundamentals of the numerical calculation method and its capability of calculating two-dimensional discharge flow from a pipe. This calculation technique is able to treat effects of flow contraction at the pipe inlet and flow expansion at the exit upon discharge