Coupled hydrodynamic modelling of flow field–electrode interactions in redox flow batteries

Vanadium redox flow batteries (VRFBs) are a promising technology for large-scale energy storage, yet the hydrodynamic coupling between flow fields and porous electrodes remains poorly understood and strongly influences electrolyte distribution and pressure loss. A key challenge in VRFB design is achieving uniform electrolyte distribution throughout the porous electrode while minimising hydraulic losses and pumping requirements. To address this challenge, this work develops a novel three-dimensional multi-region computational framework in OpenFOAM to resolve coupled hydrodynamics in free-flow channels and porous electrodes. The framework employs Beavers–Joseph interface conditions together with a three-zone electrode compression representation to capture under-rib, under-channel, and intrusion regions. The study focuses on hydrodynamics, establishing a validated Darcy-based foundation for future coupled transport and electrochemical modelling. The framework is rigorously validated against published numerical benchmarks and experimental pressure-drop measurements, demonstrating strong predictive capability across different operating conditions and geometries. Results show that interdigitated flow fields provide better hydraulic performance compared with serpentine configurations, achieving higher mean electrode velocity per unit pressure drop and promoting more effective electrolyte penetration into the porous electrode. However, electrolyte distribution uniformity and hydraulic efficiency are shown to depend strongly on flow-field geometry and electrode compression, highlighting the importance of geometry-resolved modelling for design optimisation. Remaining discrepancies are primarily associated with the assumption of isotropic permeability and the omission of inertial corrections at elevated flow rates. Overall, the framework provides a computationally efficient and physically grounded tool for analysing and optimising flow-field architectures in VRFBs, supporting improved hydraulic efficiency, and reduced pressure losses.