critical wind speed of flutter

例句：

1. 1.
   鸟等的
2. 2.
   因风力大而
3. 3.
   尤指在飞机上
4. 4.
   尤指在飞行中
5. 1.The bird fluttered its wings in the wind.
   那只鸟在风中扑动翅膀。
6. 2.The plane fluttered dangerously as it tried to land.
   飞机在试图降落时剧烈摇晃。
7. 3. The butterfly fluttered its wings in the sunlight.
   蝴蝶在阳光下扑动翅膀。