Analysis of Fluid Suction Characteristics of Polyhedral Particles in Deep-Sea Hydraulic Collection Method

Deep-sea hydraulic collection is a key technology for seabed mineral resource extraction, offering higher efficiency and environmental protection compared to other collection methods. However, due to their complex characteristics, the suction properties and influencing factors of polyhedral particles in hydraulic suction collection remain elusive. This study utilized dimensionless methods and conducted experiments to analyze the flow characteristics in cone-shaped collection hoods and the distribution of suction force on polyhedral particles, and researched the effect of various parameters, such as Phi, H/R, R/S, and H/dp (referring to the nomenclature given in the last part of this paper), on the suction force coefficients of polyhedral particles based on the suction force coefficients of spheres by acquiring the suction coefficient ratio (kc). The results indicate the following: (1) the presence of suction and coherent vortices in the horizontal positions of 0.1R to 0.2R within the central region, which move with changes in pump suction or cove height, benefiting particle collection; (2) the particle suction force (Fd) decreases with increasing sphericity (Phi), with a more pronounced decline in high-speed flow fields, exhibiting two peaks and one trough in the Fd curve within the hood's flow field; (3) the kc generally increases with decreasing Phi at the same collection position, showing increasingly stable fluctuations, and kc is sensitive to surrounding flow velocities with a rapid growth trend at higher speed, revealing that the suction coefficient (Cd) of polyhedral particles is significantly larger than that of spherical particles with increasing flow speed in high-speed flow fields; (4) Fd decreases with increasing H/dp, with a noticeable slowdown when H/dp exceeds 3.5. This study reveals the force characteristics and influencing factors of non-spherical coarse particles in hydraulic suction collection flow fields, providing insights for the development of collection technologies and equipment for deep-sea solid mineral resources, particularly irregular coarse particles.