Abstract: To study the cavitation mechanics and its relation- ship with noise characteristics of the valve-port high-speed flow, high-speed photography and noise spectrum analysis are applied to investigate the flow area and the related phenomenon inside the throttling area of valves. The observation is taken under macroshot-model and the frame rate of high-speed camera can reach 120 000 frames/s. Both the experimental and the nume- rical results reveal that the cavitation inception and flow separation have close relationship with the pressure distribution in the valve. As the secondary influencing factor, the change of inlet-pressure also affects the characteristics of cavitation and noise. To deep orifice, the position of cavitation inception is invariably near the sharp-edged area, where the throttling-edge crosses the side-wall of the orifice, and the inception position slightly changes with the change of valve opening. Spectrum analysis indicates that the size and shape of cavitations are also the most important factors which affect the noise.

Key words: Cavitation, High-speed photography, Noise characteristics, Orifice, Pressure distribution