free-air flow的用法和样例：
例句
- Propeller fans are used to move free air within a room or through channels having low frictional resistance.
螺旋桨式风机通常用于房间内或通过风道时移动自由气流时，产生微弱的摩擦阻力。 - This turbulence caused the flow pattern in the tunnel to be similar to the flow pattern in free air at a higher Reynolds number.
这种紊流使风洞内的流谱与在较高的雷诺数下自由气流中的流谱相似。
