Topology Based Multiphase Flow Model for Nuclear Safety Applications

Computing the working conditions and transient processes of nuclear reactors is important for both the safety and design of these reactors. The operation of nuclear reactors depends on various phenomena resulting from different flow regimes in the core. To accurately describe the system's operation, multiphase, multi-scale models should be integrated for dispersed and separate flow topologies. This work presents a new multiphase flow model which accounts for the actual flow topology (dispersed or separate) and provides a unified model for all flow regimens. The basis of the new model is a physical insight that guides the averaging process of the multiphase conservation equations. The study defines a topology function for each fluid which expresses its connectivity on the scale of the computation grid. The new topological function is used to divide the mixture's averaged conservation equations into phasic equations in a way which correctly accounts for stress and heat transfers in the mixture. From this perspective, we show a unified model which is able to correctly describe the interactions between the phases in the flow field. This model can provide the flow starting from dispersed conditions and moving to separate flows.