Numerical evaluation on the flow field and drag force inside and around a ship-type truss aquaculture cage

The present analysis examines the effects of net layers, inflow angles and bow geometry on the flow field and drag force of a ship-type truss aquaculture cage. The porous media method is adopted to establish the numerical ship model. To validate the accuracy of this numerical approach, the drag force and flow velocity of a net at different inflow velocities and attack angles are simulated and compared with experimental data. This paper focuses on the flow field distribution and drag variation of the cages with and without nets, and with single- and double-layer nets. Then it compares the drag force and flow field characteristics of the three ships under different inflow angles. Subsequently, the influence of bow structure on the drag and flow improvement is analysed. The results indicate that the number of net layers has little influence under head-on inflow but a strong influence under oblique and lateral inflows. Three flat-bow configurations are proposed as design alternatives for comparison with the original sharp bow. The results indicate that the flat bow produces a more uniform velocity distribution inside the ship-type truss aquaculture cage. These findings can provide insight into the hydrodynamic optimisation of ship-type truss aquaculture cages.