涡旋

       观众按下开关，观看涡旋的形成和发展趋势：越往里速度越快，形成了一个非常明显的上大下小的涡旋，具有很强的抽吸现象。涡旋有一个重要特性：在同一水平面上某点的流速与该点所处半径的乘积保持不变。即涡旋越往里速度越快，压力越小，因此涡旋具有向心抽吸的作用。

vortex

      The audience presses the switch and watch the formation and development trend of the vortex: the more inner it is, the faster the speed is, thus forming a very obvious vortex with its upper side bigger than its lower side, which has a phenomenon of very strong suction. The vortex has an important feature: on the same level, the arithmetic product of the velocity of a certain point and its radius keeps constant, that is, the more inner the vortex is, the faster the speed is and the less the pressure is, so the vortex has the action of centripetal suction.