Double-row jet detachment and initiation characteristics of polymetallic nodules and parameter optimization

Elucidating the nodule detachment-initiation mechanism in the double-row jet collection mode was a core scientific challenge for achieving high-efficiency commercial mining of deep-sea polymetallic nodules. This study systematically investigated the effects of key double-row jet parameters on sediment erosion depth, maximum nodule initiation height, detachment rate, and initiation rate through model tests and flow field analysis, thereby revealing the underlying detachment-initiation mechanism. The results demonstrated that effective nodule detachment and a significant increase in initiation height were achieved under the optimal combination of collection parameters. For instance, the maximum initiation height and a peak detachment rate up to 73.33 % were attained when the jet velocity ( V j ), nozzle height ( H ) jet angle ( θ ), nozzle spacing ( B ) and travel speed ( V t ) were 8–10 m·s −1 , 45 mm, 45–55°, 190–200 mm, and below 0.4 m·s −1 , respectively. Furthermore, experimental data analysis confirmed a significantly positive correlation between sediment erosion depth and nodule detachment-initiation characteristics. This study clarified the mechanistic role of double-row jet parameters in the nodule detachment-initiation process, providing a quantitative theoretical foundation for the precise optimization and efficient operation of double-row jet collection equipment for deep-sea polymetallic nodules.