Performance of a NACA 63₄-021 hydrofoil in motion under and in close proximity of a free surface for a large range of angles of attack is studied. Lift and drag coefficients of the hydrofoil at different submergence depths are investigated both numerically and experimentally, for 0° ≤ AoA≤30° at a Reynolds number of 10⁵. The results of the numerical study are in good agreement with the experimental results. The agreement confirms the new finding that for a submerged hydrofoil operating at high angles of attack close to a free surface, the interaction between the hydrofoil-motion induced waves on the free surface and the hydrofoil results in mitigation of the flow separation characteristics on the suction side of the foil and delay in stall, and improvement in hydrofoil performance. In comparing with a baseline case, results suggest a 55% increase in maximum lift coefficient and 90% average improvement in performance for, based on the lift-to-drag ratio, but it is also observed significant decrease of lift-to-drag ratio at lower angles of attack. Flow details obtained from combined finite volume and volume of fluid numerical methods provide insight into the underlying enhancement mechanism, involving interaction between the hydrofoil and the free surface.

研究了NACA 63 ₄ -021水翼在大迎角范围内在自由表面下和附近自由运动的性能。在雷诺数为10 ^5的情况下，对于0°≤AoA≤30°的水面，在不同浸没深度下的升力和阻力系数均通过数值和实验研究。数值研究结果与实验结果吻合良好。该协议证实了新发现，即对于在接近自由表面的高攻角下工作的水下翼型，自由表面上的翼型运动感应波与翼型之间的相互作用会减轻吸油口的流动分离特性。箔的一面，延缓失速，并改善水翼性能。与基线情况相比，结果表明，基于升阻比，最大升力系数增加了55％，而性能平均提高了90％，但是还发现，升阻比明显降低了在较低的攻角下。