Hydrodynamic interactions in midwater trawl nets: combined effects of flow velocity and door spreading through numerical and experimental approaches

Owing to escalating fuel costs and dwindling fish stocks, optimising midwater trawl efficiency requires a thorough investigation of net design variables. To understand the morphological changes in a trawl net under different operating conditions, a numerical model of the trawl was established using the lumped-mass method. The effects of door spread and flow velocity on trawl morphology, drag force, and energy consumption coefficients were analysed. A generalised additive model was employed to predict the net configuration. In addition, the net mouth parameters of the trawl net were measured using scale model tests in a towing tank and full-scale sea trials to verify the reliability of the predicted results. This study provides guidelines for improving the geometric performance and catchability of midwater trawls.