Parameter optimization of a double-deflector rectangular cambered otter board: Numerical simulation study

An otter board is an important device that provides a desired horizontal opening of a trawl net. A high lift-to-drag ratio is required for an otter board to maintain fishing efficiency. This study optimized the parameters of a double-deflector rectangular cambered otter board based on the maximum lift coefficient and lift-to-drag ratio and studied the hydrodynamic performance of the optimal otter board. Computational fluid dynamics (CFD) analysis was used (verified by a flume tank experiment) in the optimization process. Simulation results showed that the aspect ratios and deflectors had a significant influence on the hydrodynamic performance of an otter board. The optimal otter board had a better performance when the aspect ratio was 1.4 and the cambered ratios of the deflectors were 10%. Its maximum lift-to-drag ratio was 4.835, which was 1.10 times that of the initial otter board. The streamlines around the otter board showed that the structure of the deflectors can delay flow separation. The range of the wing-tip vortex increased with the angle of attack until stall occurred at which time the vortex began to break down.