Effects of aspect ratio on the hydrodynamic performance of full-scale rectangular otter board: Numerical simulation study. (15th September 2017) - Xu, Qing Chang
Abstract: In the present work, the hydrodynamic characteristics of full-scale rectangular otter board were studied by numerical simulation, including the effects of aspect ratios (AR), flow distribution around the otter board, induced velocity, induced angle of attack (AOA), effective AOA and induced drag coefficient. It was demonstrated that the otter board had a critical AOA of 40° (when the stall appeared) and induced AOA of 3~10°. The maximum induced drag coefficient was 0.185, which is a great contribution to the total drag coefficient. The otter board exhibited better performance when the AR was set to 0.5, and higher AR had a smaller critical AOA (the stall happened earlier). The maximum lift coefficient decreased with an increasing AR, while the maximum lift-to-drag ratio increased. The induced drag coefficients showed similar trends across ARs, initially rising with an increase of the AOA, and then dropping. The flow distribution around the otter board showed that the wing-tip vortex was fully developed at the AOA of 40°, and the AR can affect the development of the wing-tip vortex. Highlights: Hydrodynamic performance of rectangular otter boards was studied with CFD. For these boards, the optimum aspect ratio (AR) is 0.5. Above AR of 0.5, smaller critical angles of attack occur (the stall happens earlier). Maximum lift-to-drag ratio increases and lift coefficient decreases with increasing AR.