Multidimensional two-fluid model numerical simulation of bubbly column flow in a water pool with obstacle

Abstract

Investigation of two-phase flow around obstacles is important for thermal-hydraulic design and safety analyses of various equipments in nuclear power plants. The examples of obstacles are spacers in nuclear fuel rod bundles or in steam generator tube bundles, as well as perforated plates submerged in two-phase mixture in order to equalize void fraction and swell level spatial distribution in large volumes. In this paper the numerical simulation of a bubble column flow in a rectangular water pool is performed. The gas is injected in form of bubbles near the pool bottom through the short perforated pipe. A horizontal plate with a slit is introduced at the half-length of the pool and it forms an obstacle to the bubble column flow. The simulation is performed with the multidimensional transient two-fluid model. The model is based on the mass and momentum balance equations for the liquid and gas phase. The model is numerically solved with the application of the SIMPLE type algorithm developed for the conditions of two-phase flow. Obtained results show the ability of the applied modelling approach to simulate complex liquid and gas flow conditions around obstacles. The bubble column rise along the pool and passing through the plate slit is shown, together with the recirculation of water

below and above the horizontal plate. The problem of achieving symmetric velocity and void fraction fields for symmetric rectangular pool geometry and boundary conditions is encountered. The simulations without and with the lateral force are performed, showing the importance of lateral force inclusion in the momentum balance equations.