Hydrodynamic performance of semi-pelagic self-adjusting otter boards in demersal trawl fisheries

In this study, we show how a novel self-adjusting, semi-pelagic otter board have high hydrodynamic efficiency and reduce seabed contact. The boards two adjustable flaps, which are controlled by on-board altimeters actuators, modifying their lift drag altering position in the water column. actuators governed Proportional Integral Derivative feedback system, uses altimeter data to maintain at preset target height above seabed. Full-scale experimental trials were conducted measure performance of new design system compare it with conventional seabed-contacting design. We demonstrate that is highly efficient has lift/drag ratio 4.2, 3.5 times boards. When was set 1 m, SAO contacted most 16% time; decreased 8% when raised 2 m seabed; there no contact 5 10 m.