Vibrating in the wind, the bristles create some drag. But they also reduce the wing's slipstream, an area of low-pressure turbulence that pulls back on the wing, and hence reduce drag.
The combination of low pressure on one side and high pressure on the other creates a drag force that must be overcome — a significant waste of energy.
为此，必须浪费大量能源以克服压力差产生的拉力。
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The low-pressure area reduces wind resistance and hence the amount of drag, which means less energy is needed to maintain the same speed as the leader.