Experimental investigation on the water-entry characteristics of the structure passing through the broken ice field

In this study, experiments are conducted on the process of a structure entering water under an ice-free environment and a broken ice field environment with three different broken ice densities based on a water-entry experimental platform. The influences of the broken ice field environment and different broken ice densities on the variations in the cavity morphology and movement features of water entry into the structure are investigated. The results show that the broken ice field environment postpones the surface closure of the cavity, leading to an increase in the size of the closed cavity, which, in turn, affects the cavity collapse process, slows down the overall collapse of the cavity, and is conducive to the cavity formation of the structure. In addition, when the density of broken ice is 30%, the influence of the broken ice field on the variations in the cavity morphology is not significant. When the density of broken ice increases to 70%, the expansion, cavity closure, and collapse are significantly different from those in an ice-free environment. Necking and deep closure occur. Some broken ice is drawn into the cavity, accelerating the cavity collapse. The effect of the broken ice field environment on the motion stability of the structure entering the water increases with an increase in broken ice density. When the density of broken ice increases to 50 and 70%, owing to the direct collision between the structure and broken ice, mutual forces and momentum transfer are generated. This results in a horizontal displacement of the trajectory of the structure, a sudden decrease in velocity, and an acceleration of velocity attenuation, ultimately affecting the motion stability and drag reduction characteristics of the structure.