At time t=t0, the setting of the blades is changed suddenly such that they assume the position denoted by the solid blades, perturbing the mass flow in a one-dimensional sense.

• 当t＝t0时，叶栅的位置突然改变，因此取代实心叶片所标示的位置，在一维的意义上干扰了质量流动。