free vortex flow

例句：

1. 1.The free vortex flow in the tunnel is responsible for reducing friction and increasing efficiency.
   隧道中的自由涡流流动负责减少摩擦并提高效率。
2. 2. In the free vortex flow, the particles move rapidly and efficiently.
   在自由涡流流动中，粒子移动迅速且高效。
3. 3. The free vortex flow has been studied extensively in fluid dynamics research.
   流体动力学研究中广泛研究了自由涡流流动。