The vortex wake and its induced velocity of a helicopter rotor operating near the ground at low forward speeds have been studied using a simplified free wake-ground vortex model.

本文用一简化自由涡模型模拟旋翼尾涡系，用一简单涡模拟地面涡，对近地低速飞行时旋翼尾涡系的畸变及其引起的诱导速度变化作了研究。

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Once established, the heat content of the air at ground level is enough to keep the vortex going.

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And I wish that we could just have a time machine and sort of vortex ourselves from place to place, but we are definitely going to cover the ground and get to Texas.

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