Large eddy simulation in hydraulic valves

Cavitation in hydraulic spool valves involves large-scale vortical structures in an unsteady submerged jet. According to engineers from Purdue University, current CFD approaches do not accurately predict these unsteady vortices, nor do they properly account for bubble-dynamics/flow-structure interactions.

Valves are an important component in hydraulic systems to control flow and pressure. The spool valve is often used in fluid-power systems. It consists of a spool moving along its axis within a cylinder. The hydraulic fluid is supplied to an upstream chamber and is metered through the spool valve orifice to a downstream chamber in the form of an unsteady turbulent jet. The large pressure drop across the orifice can result in cavitation in the valve chambers or the cylinder itself, which can reduce the hydraulic efficiency of the valve and also lead to significant pitting and erosion if the cavitation bubbles implode near solid surfaces.

Current CFD approaches for turbulent flows involve determination of the mean velocity and pressure field by solving the Reynolds-averaged Navier-Stokes (RANS) equations and have been used for evaluation of flow forces. For cavitation modeling, the location of the minimum mean pressure, as predicted from a single-phase flow calculation, is often assumed to be indicative of cavitation inception. This approach does not account for the bubble-dynamics/flow-structure interactions or the possibility that cavitation may occur in the cores of vortical structures.