A fluid–structure interaction (FSI) solver for evaluating the impact of circular fish swimming patterns on offshore aquaculture

Fish swimming behaviour involves complex fluid–structure interactions (FSI) with significant impacts on offshore aquaculture environments. This study presents a three-dimensional FSI module integrated into the open-source computational fluid dynamics code OpenFOAM, specifically designed to simulate circular swimming behaviours of fish within offshore aquaculture environments. The module adopts immersed boundary (IB) method to capture the complex interactions between multiple swimming fish and their surrounding fluid environment. The model incorporates realistic fish motion based on rainbow trout kinematics to simulate circular swimming patterns. The convection–diffusion equation is integrated to investigate the distributions of dissolved oxygen (DO) influenced by swimming-induced flow fields. Validations against experimental data confirmed the module’s reliability in predicting disturbed velocity profiles and drag forces acting on moving objects. The simulated results highlight that circular swimming generates distinct vortex structures, enhancing water mixing, and significantly improving oxygen distribution in regions of poor circulation. These findings indicate that this FSI module is a robust tool for studying fish swimming behaviours and can be used to predict the potential impacts of fish swimming on aquaculture cages. • New IB-based FSI module in OpenFOAM simulates circular fish swimming in aquaculture. • Validation shows excellent agreement for velocity profiles and drag forces. • Circular swimming affects flow via vortex formation. • Shorter undulation periods yield higher TKE, promoting oxygen distribution.