Effect of wingtip flow on hydrodynamic characteristics of cambered otter board

Abstract The hydrodynamic characteristics of cambered otter boards with a camber ratio of 15% and aspect ratios of 0.5, 1.0, 1.5, and 2.0 were investigated through flume tank experiments and CFD analysis for the cases in which the wingtips were blocked or unblocked. In the blocked wingtip case, the maximum lift coefficient, stall angle, and lift slope (α: 0° to 15°) were approximately 1.75, 15°, and 0.115 (deg−1), respectively, regardless of the aspect ratio. Comparatively, in the unblocked wingtip case, maximum lift coefficients were 1.74 (stall angle: 40°), 1.65 (35°), 1.54 (25°), and 1.50 (20°), and the lift slope increased from 0.063 to 0.097 (deg−1) as the aspect ratio increased from 0.5 to 2.0. The drag coefficients for all unblocked wingtip models were larger for all considered angles of attack. The effect of the wingtip flow formed around the otter board on the hydrodynamic characteristics was visualized using CFD analysis. A small-scale wingtip plate with a width of 0.1c was designed. Particularly, for boards with aspect ratios of 1.0–1.5 and a 0.1c wingtip plate, lift slopes and maximum lift coefficients approached those for the blocked wingtip cases, and stall angles were close to those for the unblocked wingtip cases.