Experimental investigations of cavitation effects on flow characteristics of small orifices and valves in water hydraulics

The flow characteristics and cavitation effects of water passing through small sharp-edged cylindrical orifices and valves of different shapes in water hydraulics are investigated. The test results using orifices with different aspect ratios and different diameters show that the flow coefficients in the case of non-cavitating flow are larger than that of flow in the case of cavitation occurrence. The flow coefficients of flow with cavitation initially decrease as Reynolds number increases and ultimately tend to be of constant values close to contraction coefficient. Large aspect ratio has an effect of suppressing cavitation. The experimental results about disc valves illustrate that the valves with sharp edge at large opening are less affected by cavitation than that at small opening. Throttle with triangle notch has better anti-cavitation ability than that with square notch. The flowrate of the throttle with square notch is significantly affected by the flow direction or the flow passage shape.