Study on influence of pit defects on cavitation flow characteristics of throat of thick orifice plates

Various valves, orifice plates and other throttling parts in the pipeline system will experience hydraulic cavitation as the pressure difference increases before and after the system works, which will seriously affect the working performance and safety of the system. The critical pressure ratio of cavitation of a thick orifice plate and the influence of pits on the critical pressure ratio of cavitation of an orifice plate were explored through numerical simulation. Furthermore, the cavitation flow characteristics under the coupling of pits and cavitation were further studied, and the mechanism of cavitation collapse under the action of pits was elucidated. The results show that cavitation occurs only when the ratio of orifice outlet pressure to inlet pressure is less than 0.5. The pit has the effect of promoting the primary-development-collapse evolution behaviour of cavitation bubbles, and a single small pit has almost no effect on the critical pressure ratio of cavitation, but the pit tends to increase the critical pressure ratio of cavitation. When the pressure ratio is near the critical pressure ratio of cavitation, the pressure peaks at each point appear on the pit side of the pit-free orifice plate and the pit side of the pit defective orifice plate, accompanied by periodic cavitation. In the safety design of liquid pipelines and valves, the risk of cavitation under the cavitation critical pressure ratio and the hazard of pipeline wall thinning caused by cavitation and ablation of pit defects should be considered. © 2023 Materials China. All rights reserved.