Simulation of two-phase flow in network mixers using periodic boundary conditions

• A water-in-oil churn flow was modelled using a reduced geometric model. • LoopNUB uses periodic boundary conditions between the inlets and outlets. • The entrance effect is not modelled using inlet–outlet periodic conditions. • LoopNUB predicts the fully developed flow regions of extended networks. • Simulation of two-phase flow using LoopNUB is verified and validated. NETmix is a network mixer comprising mixing chambers interconnected by channels. Recently, a reduced geometry CFD model, the LoopNUB, was introduced for simulating single-phase flow with heat transfer in NETmix by imposing periodic conditions around the four unit cells of the network. This work proposes using LoopNUB, reducing the simulation domain by 2.3 compared to the geometry (ExtendedNUB) previously used to simulate two-phase flow. A water-in-oil churn flow was modelled. The flow patterns and critical aspects related to two-phase mixing obtained with LoopNUB are similar to those obtained in downstream chambers of ExtendedNUB, proving the flow periodicity in NETmix and the ability of LoopNUB to reduce the simulation domain also for multiphase flows. The LoopNUB does not simulate entrance effects, observed in the first three rows of the network, but provides a better description of the fully developed flow regions, which account for more than 90% of an industrial reactor.