Prediction of hydraulic inductance

The dynamic response, stability and fluid-borne noise characteristics of fluid power components and systems can be strongly influenced by the inertia or 'hydraulic inductance' of the fluid in passageways, which are often of complex geometry. The hydraulic inductance is a parameter that has often proved to be very difficult to quantify accurately, either theoretically or experimentally. This paper presents a method of numerical calculation of the hydraulic inductance in a passageway. The method is simple to apply and can be applied to geometries of arbitrary complexity. A simple way of using a Computational Fluid Dynamics package for calculating hydraulic inductance is also demonstrated. Results are presented for a simple cylindrical orifice, a simple spool valve and a conical poppet valve. The effect of the inductance on the response of a poppet valve is demonstrated.