Study on relationship between angular nozzles parameters and jet cavitation characteristics under submerged conditions

In order to optimize the key equipment for deep-sea aquaculture cage netting cleaning, based on the cavitation jet principle, we investigated the influence of different geometric parameters of angular nozzles on cavitation jet characteristics to provide a reference for the optimal design of high-efficiency cleaning nozzles. We employed numerical simulation of cavitation water jets for angular nozzles using the Reynolds-Averaged Navier-Stokes (RANS) equations coupled with the Realizable k-ε Turbulence Model, the Volume of Fluid (VOF) Multiphase Flow Model, and the Schnerr-Sauer Cavitation Model. Besides, we designed 25 nozzle schemes with different structural parameters using an orthogonal experimental approach, and analyzed the effects of six parameters (Contraction length, cylindrical section length, diffusion section length, throat diameter, contraction angle, and expansion angle) on cavitation performance. The results indicate that the parameters ranked in descending order of influence on collapse distance: cylindrical section diameter d>diverging angle θ>contraction length L₂>diverging section length L₄>cylindrical section length L₃>converging angle $\alpha$; while for vapor volume fraction: cylindrical section diameter d>diverging angle θ>diverging section length L₄>converging angle α>contraction length L₂>cylindrical section length $L_3$. The cylindrical section diameter $d$ was the dominant parameter affecting cavitation characteristics and exhibited a monotonic variation trend; the cylindrical section length $L_3$ had an optimum value; whereas the contraction length $L_2$, diverging section length $L_4$, and converging angle $\alpha$ showed significant non-monotonic variations, reflecting complex interactions among the parameters.