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1·The air flowing over a bird's wings curls upwards behind the wingtips, a phenomenon known as upwash.

流过鸟翅膀的空气在翼尖后向上流动，这种现象被称为上升流。

2·Other birds flying in the upwash experience reduced drag, and spend less energy propelling themselves.

其他鸟类在上升流中飞行时受到的阻力减小了，它们在推动自身前进时消耗的能量也减少了。

3·The air flowing over a bird’s wings curls upwards behind the wingtips, a phenomenon known as upwash.

气流在划过鸟类双翼时会在其后面弯曲向上，这是一种叫上升流的现象。