ABSTRACT
In fact, the momentum of the fluid flowing through the valve varys two times, (See Fig. 1 ) . The first variation is in the process from inlet to throttle port , the second is in that from throttle port to outlet. In past time only the flow force engendered by the first variation of momentum is considered and that engendered by the second variation of momentum is neglected. Through study, it is found that the second variation of the momentum has different affection on steady state flow force between the diverged flow and the converged flow.
