Numerical Investigation of Flow Regulation Using a Skew Branch Pipe in Aquaculture Vessel Pipeline Systems

Guoxin No. 1, one of the largest smart aquaculture vessels currently in operation, represents an important development in large-scale mobile aquaculture platforms. Continuous circulation of oxygen-rich seawater is essential for maintaining suitable culture conditions in intensive aquaculture vessels. However, the complex pipeline arrangements used for distributing seawater among multiple farming tanks can result in uneven flow allocation. In this study, three-dimensional CFD simulations were conducted to investigate the internal flow behaviors and flow distribution in a T-type pipeline system for an aquaculture vessel. Extending previous studies based on coplanar branch configurations, a non-coplanar skew branch pipe arranged in the xy-plane was investigated. Particular attention was given to the influence of the spatial offset between the branch pipe and the main pipeline axis on velocity distribution, pressure variation, and outlet flow rates. The results show that the spatial offset modifies the momentum transfer process at the junction and generates a swirling motion inside the main pipeline. Compared with the conventional inclined branch configuration, the offset branch shifts the high-velocity core away from the pipe center and reduces the imbalance between the two outlet flow rates. The pressure field is also redistributed due to the asymmetric momentum injection, indicating a trade-off between improved flow uniformity and local pressure variation. The present study demonstrates the potential of non-coplanar skew branch configurations as a passive approach for improving seawater distribution in large-scale aquaculture vessel pipeline systems.