Numerical Analysis of Transient Flow through a Pipe Orifice. 1st Report, Time Constant for the Settling Flow.

Abstract

As a fundamental consideration in hydraulic valve dynamics, transient flow through a pipe orifice has been studied via numerical analysis. Steady axisymmetric viscous fluid flow was first investigated to confirm the present SIMPLER-based finite volume methodology. Time-dependent calculation for a suddenly imposed pressure gradient has shown two distinct characteristic time constants for the transient state. The first characteristic time constant is commonly considered corresponding to the flow rate change, while the second one concerning the variation of flow structure has not been investigated in earlier studies. The final settling of the flow is established through the second characteristic time which is almost ten times larger than the first one for the present condition.