Effect of deflector angle on hydrodynamic performances of a double-slotted cambered otter-board

The effect of deflector angle on hydrodynamic performances of a double-slotted cambered otter-board is investigated using engineering models in a wind tunnel. Three different angle combinations (35°-30°, 30°-25°and 25°-20°) are evaluated at a wind speed of 28 m/s. Parameters measured included: drag coefficient Cx, lift coefficient Cy, pitch moment coefficient Cm, center of pressure coefficient Cp, over a range of angle of attack (0° to 70°). These coefficients are used in analyzing the differences in the performance among the three otter-board models. Results shows that the maximum lift coefficient Cy of the otter-board model with the angle combination (35°-30°) of two deflectors is the highest (2.160 at a=55°). The maximum Cy/Cx of the otter-board with the angle combination (25°-20°) is the highest (3.842 at a=2.5°). A comparative analysis of Cm and Cp shows that the stability of otter-board model with the angle combination (25°-20°) is better in pitch, and the stability of otter-board model with the angle combination (30°-25°) is better in roll. The findings of this study can offer useful reference data for the structural optimization of otter-boards for trawling