Abstract: This paper presents a study of a flow and pressure regulating valve of DN200 type, using numerical modeling that combines a realizable k-ε turbulence model with a Zwart-Gerber-Belamri cavitation model. We focus on the cavitating characteristics of flows in the valve with small, medium and large openings, and the effects of valve opening and inlet-outlet pressure difference on these characteristics. The results show that high pressure and large velocity gradients occur in the orifice, flow separation appears near its inlet edge, and wall attaching shear vortices form at the wall. Flow separation and generation of these vortices are the mechanism of flow cavitating in the orifice. Under fixed inlet and outlet pressures, the total volume of cavitation bubbles increases linearly with valve opening, while cavitation strength varies insignificantly. As the cavitation coefficient is decreasing, the flow coefficient keeps stable first, then increases slightly, but decreases sharply after that. The results are useful for the structural optimization and operation maintenance of DN200 valves.

Key words: flow and pressure regulating valve, cavitation, flow separation, wall attaching vortex, cavitation coefficient, flow coefficient