Hydrodynamic performance of windsurfing boards with bottom modifications at high speed in calm water

Hydrodynamic performance of windsurfing boards is greatly affected by geometrical details of their bottom surfaces. In this study, computational fluid dynamics is applied to simulate flow around boards with several bottom modifications, including deadrise, rocker, step, wedge, and wing-tail profile. These simulations are conducted in steady-state, calm-water regimes at high planing speeds. It is found that at similar board trim angles and vertical positions, the largest lift is produced by setups with the bottom wedge and the wing-tail profile that enhance the downward deflection of the incident water flow. The highest lift-drag ratio is achieved by the variants with the bottom step and wedge that enable partial air ventilation of the bottom surface, which leads to reduced wetted surface and lower frictional resistance. The center of lift is located more forward on the rocker and stepped configurations, while it is positioned more rearward for the wedge and wing-tail setups. The obtained results can be used for guiding board designs aimed at maximizing the board hydrodynamic performance in calm water.