This, the researchers believe, is caused by the surface of the water smoothing out a vortex of air coming off the flying fish and reducing drag.

研究者相信，这源于水面平滑了飞鱼迎面的风涡，降低了阻力。

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The surface of propeller and its trailing vortex is divided into a number of small hyperboloidal quadrilateral panels with constant source sink and doublet distributions.

螺旋桨表面和它的尾涡面离散为四边形双曲面元，每个面元上布置等强度偶极子和源汇分布。

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The results show that the interaction between a viscous vortex ring and a free surface is different from the inviscid one.

结果表明：由于粘性的存在，使得涡环与自由表面的相互作用与无粘情形相比有许多不同。

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The vortex generators themselves are pins or vanes that protrude from the surface and set up microscopic eddies in the boundary layer.

ECONOMIST: The turbulent world of swimming