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.

The vigorous development of China's mariculture industry has led to an increasingly urgent demand for high-performance auxiliary vessels. Taking a multi-functional aquaculture auxiliary catamaran as the research object, this paper uses the boundary element numerical method based on three-dimensional potential flow theory for numerical prediction. It presents the numerical simulation results of the catamaran's motion responses and the surface elevation between hulls under various loading conditions, sea states, sailing speeds, and wave directions, aiming to reveal its motion response patterns under complex sea conditions. The results indicate that under sea states 2 and 3, the seakeeping performance of the catamaran consistently showed the characteristics of being worst under light load, best under full load, and intermediate under half load. Wave direction had a significant impact on motion responses of the catamaran, with beam seas being the most unfavorable condition, leading to a significant increase in roll amplitude. The variation in ship speed exerted distinct effects on the motion responses in all directions under sea states 2 and 3, but its influence was limited under beam sea condition. The characteristics of surfaceelevation were significantly affected by draft, wave conditions, and speed. An increase in speed caused the resonant frequency at the peak of surface elevation to shift towards higher frequencies, while a decrease in draft could lead to significant surface elevation under specific coupled conditions of speed and wave state. Therefore, when sailing under light load condition, the catamaran should carefully plan its route and speed to avoid excessive motion responses and surface elevations.