When a fluid flows in a pipe, it moves fastest at the center of the pipe and slowest at the wall because of friction between the pipe and the flowing fluid?

• 当流体在管内流动时，靠近管子中心的流体流动速度最快，而靠近管壁的流体流动速度最慢，因为在流动的液体和管壁间有摩擦力。