Experimental investigation of critical suction velocity of coarse solid particles in hydraulic collecting

Hydraulic collecting and pipe transportation are regarded as an efficient way for exploiting submarine mineral resources such as the manganese nodules and ores. Coarse particles on the surface of the sea bed are sucked by a pipe during the mining and crushing of the mineral. In this paper, the critical suction velocity for lifting the coarse particles is investigated through a series of laboratory experiments, and the solid–liquid two-phase flow characteristics are obtained. Based on the dimensional analysis, the geometric similarity is found between actual exploitation process and model test with the same kind of material. The controlling dimensionless parameters such as the hydraulic collecting number, the relative coarse particle diameter, the relative suction height, and the density ratio are deduced and discussed. The results show that the logarithm in base 10 of the hydraulic collecting number increases approximately linearly with the increase of the relative suction height, while decreases with the relative particle diameter. A fitting formula for predicting the critical suction velocity is presented according to the experimental results. Graphic abstract