Evaluation of Wave-induced Coupled Dynamics Between Multi-purpose Offshore Supply Vessel and Suspended Load During Crane Lifting Operation

-Part 2 Analysis for Wave-induced Coupled Dynamics Right After Suspended Load Entry into the Water-

Abstract

As crane lifting operation in ocean is vital to construct offshore structures and install subsea facilities on the seafloor, evaluation of safety and availability for the crane lifting operation is needed before the construction. For these analyses, it's fundamental to predict wave-induced coupled dynamics between a vessel and a suspended load. The coupled dynamics makes the each mechanics more complex. In the case of using the multi purpose offshore supply vessel to the crane lifting operation, deep understanding about the mechanics is required because it offers various crane operations. In our previous paper, we propsed the numerical method to estimate the swirling of the suspended load in air and considered the impact of the suspended load's location on the coupled dynamics using the both numerical calculation and estimation method. To expand our knowledge and numerical method for the crane operation, we inestigated the coupled dynamics right after the suspended load entry into the sea surface. In such the situation, it's possible that the hydrodynamics on the suspended load change the coupled dynamics and produce unexpected risk for the crane lifting operation. In this paper both experiments and numerical simulation we conducted are shown to consider the coupled dynamics between the vessel and the suspended load. Furthermore we indicated the results of sensitivity analysis by numerical simulation to put the point of focus on the natural period of the vessel's roll motion. As results, we made clear the inversion of the natural period could be occured depending on where the location of the suspended load is.