CFD–DEM-based design and optimization of a new mechanical collector for deep-sea nodules

With the sustained growth in demand for battery-metal resources, global attention is shifting to the commercial development of deep-sea nodules. To address the large environmental disturbance, structural complexity, or scale limitations of mainstream collection methods, this study validates a novel rotary-rake mechanical collector using a coupled computational fluid dynamics and discrete element method (CFD-DEM) approach. Under representative mining conditions, we elucidate the operating principle of the rotary-rake collection process and establish a design methodology for key parameters. The compound motion of rake-tine components is captured with an overset-grid method, and simulations analyze near-bed flow dynamics under different rotational and traveling speeds. Focusing on collection performance and landing-position distribution, we further obtain optimized parameters for optimal nodule collection and provide guidance for stacking-zone layout. Finally, water-tank experiments with mixed-size nodules corroborated the coupled CFD-DEM results. Results indicate that, within the selected operating window, increasing rotational speed has a minor effect on near-bed velocity and pressure, whereas traveling speed has a pronounced impact on the stacking-zone layout and nodule landing distribution. Under the combined constraints of low seabed disturbance and effective collection, the recommended settings are ω r = 26 rpm and v m = 0.5 m/s. This study provides a new pathway for designing efficient, low-disturbance deep-sea mining systems.