The three-dimensional cavitating flow issuing from the orifice of a ball valve was numerically investigated using the combination of RNG k-ε turbulence model and multiphase flow model. The cavitation region was predicted for axisymmetric and non-axisymmetric case when the ball moves to one side. Flow visualization experiment was conducted to capture cavitation images near the orifice of the ball valve using high-speed video camera. The predicted and observed cavitation regions agree well. Furthermore, the noise spectrums of the ball valve in cavitation and non-cavitation cases were measured. The results show that the cavitation around the orifice occurs periodically with a very high frequency of 2500 Hz. The predicted cavitation region for axisymmetric and non-axisymmetric case was compared with experimentally visualized cavitation image. It was expected that the ball vibrates in the lateral direction and cavitation occurs periodically.

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The present paper deals with the numerical analysis on unsteady flow through a spool valve. Especially the effect of the spatial and temporal grid resolutions on the computational results is investigated. For the valve model of a simple geometry, unsteady fow was calculated for the step change of the supply pressure. Variations of the fow rate and the fow force were obtained for several values of the grid resolution and the time step. Comparison of the results revealed the complex convergence process of the relevant flow analysis. The transient response corresponding to the flow rate change does not much depend on spatial grid resolution and the time step. After the transition, the fow force is strongly affected by the time step, and its convergence with the grid refinement is rather slow, while the fow rate is not sensitive to the time step and converges with a relatively rough spatial grid resolution.

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