closed vortex line

例句：

1. 1. The closedvortex line is a crucial part of the design.
   闭合涡线是设计中至关重要的一部分。
2. 2. The closed vortex line helps to reduce noise pollution.
   闭合涡线有助于减少噪音污染。
3. 3. The closed vortex line plays an important role in the flow of air.
   闭合涡线在空气流动中起着重要的作用。