Flow-particle coupling characteristics and parameter optimization of a dual-jet hydraulic collector based on Box-Behnken design

The deep-sea floor abounds with polymetallic nodules, effective exploitation of these nodules can alleviate the pressure of terrestrial resource depletion and meet industrial demands. As one of the high-efficiency hydraulic collection approaches, dual-jet technology has been widely adopted. Nevertheless, most existing studies neglect the interaction effects among multiple factors. Accordingly, this study employs the CFD-DEM model combined with the Box-Behnken Design (BBD) to systematically investigate flow-field and particle dynamic characteristics and analyze the weight of parameter influences. The results demonstrate that jet velocity is the dominant factor determining internal flow-field structures. Quantitative analysis within the investigated parameter range shows that jet velocity contributes approximately 65% to vortex formation, while collection height and nozzle spacing account for about 35%. Single-particle analysis reveals that pressure-gradient force and drag force serve as the primary driving mechanisms for particle motion, whereas the Magnus force and Saffman force mainly function at the initial jet-impact stage. Multi-particle simulations indicate that jet velocity possesses the largest influence weight, and a significant linear relationship exists between jet velocity and collection height. The optimal collection efficiency of 92.8% within the investigated parameter range can be achieved under conditions of higher jet velocity, moderate nozzle spacing and lower collection height.