中文摘要：

为了利用近水面较高的潮流流速，潮流能叶轮一般安装在接近自由面的位置，导致叶轮的水动力特性受到自由面的影响。本文基于CFD方法，通过改变叶尖浸没水深，对水平轴叶轮在自由面条件下的水动力特性展开研究。研究结果表明：叶轮轴向载荷和能量利用率平均值随叶尖浸没水深的增加而增加，并逐渐接近于无自由面时的计算结果；叶轮轴向载荷和能量利用率瞬时值产生波动，波动幅值随叶尖浸没水深的增加而减小；当叶尖浸没水深为0.79D时，轴向载荷系数及能量利用率已基本不随叶片方位角的变化而改变，即自由面已几乎无影响。研究结果可为潮流电站设计及工程应用提供依据和参考。

英文摘要：

To take advantage of the high tidal current velocity near the surface of water,a tidal current impeller is generally installed near the free surface,which influences the hydrodynamic characteristics of the impeller. Based on the CFD numerical method,hydrodynamic characteristics of horizontal axis tidal current impellers were studied in this paper,in consideration of free surface and by changing the tip- immersion. The results sho w that the average axial load and energy utilization ratio of the impeller increase with the increase of the tip- immersion,and are gradually close to the calculated results without regard to the free surface. The instantaneous axial load and energy utilization ratio of the impeller have a fluctuation. The more the tip- immersion,the smaller the wave amplitude of instanta-neous value will be. Basically,the axial load and energy utilization ratio will not change with the azimuthal change of the impeller when the tip-immersion is 0.79D . Hence, the free surface has almost no effect on hydrodynamic characteristics of impeller. The results of the study can provide a basis and reference for the design and engineering application of a tidal power station.