Hydrodynamic simulation and experiment of depth adjustable beam trawl for Antarctic krill

At present, the primary fishing method of Antarctic krill is beam trawl, in which the fishing vessel drags the beam equipped with nets through the trawl warp for midwater trawling. Due to the behavioral characteristic of collective activities, the shoal of Antarctic krill often appears in some specific depths of the sea. The existing fishing method needs to adjust the trawling depth by modifying the length of the trawl warp and the navigation speed of the vessel, which cannot adjust the trawling depth independently. To solve this problem, we proposed a depth variable device installed on the beam to adjust the trawling depth independently, aiming to track the depth where the shoal of Antarctic krill is located for accurate fishing. Investigate the hydrodynamic feature of the proposed beam trawl device by numerical analysis and water channel experiment to design the wing’s profile and determine the effective range of angle of attack. It was found that when the angle of attack of the wing is 0°–17.7°, the regulation effect of depth adjusting is better. The analysis results can be used as the parameter basis for compiling the control program for the depth variable beam.