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.

• 从钻井泵经过钻柱内部输送到钻头喷嘴的流体是一种瞬态流动，存在着压力行波，使从普通喷嘴射出的流体有一定程度的脉动。