Experimental Investigation on the Cavitation Fundamental Characteristics of a Venturi Tube Under Ambient-Pressure Conditions

The sensitivities of the cavitation inception conditions and the cavitation discharge coefficient, together with the path independence and uniqueness of inception, underpin reliable use of cavitating Venturi tube under ambient conditions. With a downstream sweep rate of 1/6 °/s verified in preliminary tests, forward and backward quasi-dynamic cavitation evolution processes were sampled to construct pressure- and flow-rate-control paths for the Venturi tube used in this study. Analysis of the control paths shows that, as the critical inlet pressure approaches infinity, the critical pressure ratio and the cavitation discharge coefficient approach characteristic values of 0.6364 and 0.5573. With ±3% practical equivalence margins, they become insensitive to the critical inlet pressure above thresholds of 2.4496 and 1.7167 MPa, respectively. The inception conditions are unique; hysteresis in the critical pressure ratio emerges for critical inlet pressures of 0.40–0.45 MPa, and path independence no longer holds for critical inlet pressure exceeding 0.45 MPa. The findings indicate that detecting and controlling Venturi cavitation under ambient conditions must account for the sensitivities and path-dependence of cavitation characteristics, and they provide a useful baseline reference.