A novel multi-module coupled algorithm for the wreck off-bottom simulation

Abstract

This paper proposes a novel multi-module coupled algorithm for the wreck off-bottom simulation (MCAWOS), involving several structures, multiple mediums, and three modules: the wreck-soil interaction module, the lifting-buffering module, and the barge-cable coupled module. In the present algorithm, the finite element method, the potential flow method and the lumped mass method are integrated and used to simulate the off-bottom process. The dynamic response characteristics of a typical salvage case with rated lifting tensions are investigated. It is found that the salvage system in waves exhibits a special breakout phenomenon, where the wreck displacements increase abruptly, and uneven distributions of the lifting tensions are observed. Case studies are conducted to further ascertain the mechanism of the breakout. As the rated lifting tension increases, the salvage efficiency rises, while the maximum roll and pitch amplitudes of the wreck decrease. Meanwhile, larger rated tension may result in more waste in equipment lifting capacity, thus 229 ton is finally selected as the appropriate preset lifting tension. In addition, when the wave direction angle increases from 90∘ to 180∘, the maximum roll value of the wreck shows a roughly decreasing trend and the planar deflection of the salvage barge relative to the wreck decreases. However, the maximum values of pitch, yaw, lifting tension and Mises seabed soil stress show irregular fluctuations. Taking all dynamic indicators into account, the wave heading interval of 150∘ to 180∘ is expected to be an ideal operating window. Conversely the 105∘ case is a dangerous state.