Fluid is conveied to bit nozzel through drill string from pump is a transient state flowing with pressure wave, which makes the fluid jetted out from nozzel has certain pulsation.

从井泵经过部输送到头喷嘴的流体一种瞬态流动，存在着压力，从普通喷嘴射出的流体有一定程度的脉动。