Water-exit impact of deep-sea mining vehicles: Experimental and numerical investigations

Abstract

The operation of the deployment and retrieval system of a deep-sea mining vehicle (DSMV) is closely related to its water exit process; rapid water exit processes under wave conditions tend to exert negative influences on the safety and reliability of the entire system. To evaluate the specific effect of the interaction between the DSMV and the surrounding seawater, computational fluid dynamics (CFD) was used to predict the hydrodynamic characteristics and water-exit impacts of the DSMV at different retrieval speeds. First, a stokes-wave-free surface based on an overset mesh method integrating the volume of fluid (VOF) method was developed to reproduce level 4 sea conditions. Subsequently, the water surface deformation and water resistance were recorded to verify the proposed numerical method. These numerical and experimental findings indicate that when a vehicle body passes through wavy water at a relatively high speed, its lifting cable experiences a water-esistance force that is several times its weight. Finally, a vehicle body with a small retrieval speed might undergo several wave cycles, resulting in its lifting cable becoming loose.