Hydrodynamic Performance of Two-Stick Stow Nets in the South China Sea

The working configuration of fixed stow nets is strongly dependent on hydrodynamic support generated by ambient flow. To clarify the hydrodynamic performance and morphological responses of a two-stick stow net used in the South China Sea, a model net was designed based on Tauti’s law, and flume-tank experiments were conducted under different flow velocities. The net configuration, net-mouth geometry, net-body deformation, and drag characteristics were analyzed. The results showed that flow velocity strongly affected net expansion, structural stability, and drag under the tested conditions. At the model scale, the stow net collapsed at 0.2 m/s but maintained a relatively complete and stable working configuration at 0.3 m/s and above, corresponding to a prototype-equivalent inflow velocity of 0.39 m/s. Therefore, the transition between collapsed and stable configurations was constrained to the interval of 0.2–0.3 m/s, and 0.39 m/s represents the lowest tested stable condition rather than a precisely determined critical threshold. With increasing flow velocity, the front section of the net body moved slightly downward, the net mouth height increased slightly, and the net mouth width decreased slightly, indicating a response pattern of vertical stretching and lateral contraction. Drag increased with flow velocity following a pronounced power–law relationship, reflecting a nonlinear increase in hydrodynamic loading. These results demonstrate the relationship between morphological adjustment and hydrodynamic loading in two-stick stow nets and provide a reference for gear design optimization, operating-period selection, and safety assessment under similar hydrodynamic conditions.