Numerical simulation of void fraction and velocity distributions in bubbly flow with two fluid model

Abstract

Investigation of two-phase flow is important for thermal-hydraulic design or improvement of reliability and safety in various kinds of thermal equipment such as steam generators, evaporators, reboilers, condensers, nuclear reactors, etc. This paper presents the numerical simulation and analyses of two-phase upward bubbly flow around obstacle, symmetricaly positioned in a rectangular channel. Two-phase flow is formed by an injection of gas bubbles near the bottom surface through short perforated pipe. Horizontal plate with slit hole is used as obstacle. It is placed at a half-height of the channel and represents obstacle to the bubbly column upward flow. The simulation is performed with the multidimensional transient two-fluid model. The model is based on the mass and momentum conservation equations for both liquid and gas phase. It is numerically solved with the application of the SIMPLE type algorithm developed for the conditions of two-phase flow. Bubbly column rises along the channel and passes through the slit hole together with recirculated water from below and above the plate. The problem of achieving symmetric velocity and void fraction fields for symmetric rectangular channel geometry and boundary conditions is encountered. The simulations are performed with and without the inclusion of the lateral force in the momentum conservation equations, showing its importance. Obtained results show the applicability of the developed model and computer code to the simulation and analyses of complex two-phase flow conditions.