counterrotating

1.The key reason for the improved performance are the pairs of counterrotating swirls created at either side of the leading-edge bumps, called tubercles.

隆起前缘能增进能关键理由，是因为在这些隆起节瘤两侧，会产生成反向旋涡流。

2.fddi不是单一环，而是两个反向旋环，每台机器能够向左右邻发送和接收数据。

Rather than being a single ring, FDDI is two counterrotating rings.Each machine can both send to and receive from each of its two neighbors.