Experimental evaluation of a mooring system simplification methodology for reducing mooring lines in a VLFS model testing at a moderate water depth

摘要

The scale model experiment for typical offshore floating structures with increasingly excessive mooring lines is usually complex and difficult to set up, which often results in low reliability of the experimental results. In the previous paper, Liang et al. (2019) proposed a mooring system simplification methodology for the scale model experiment based on the equivalent of the vessel/mooring coupled dynamics for vessel with original and simplified mooring systems and demonstrated its effectiveness by numerical studies In this paper, the feasibility of the mooring system simplification methodology is further evaluated by a model test for a very large floating structure's (VLFS's) mooring system comprising 20 mooring chains. A 10 chains simplified mooring system is obtained with the correlation coefficients of coupled vessel/mooring dynamics larger than 0.9. Thereafter, the equivalence of the original and simplified mooring systems is validated by performing the decay test, white noise test, regular and irregular wave tests. The coincidence of the model test results, including natural period, damping coefficient, response amplitude operator (RAO), motion power spectral density and motion time series of the VLFS model, confirms the equivalence of the simplified mooring system with the original mooring system and indicates that the mooring system simplification methodology is effective in designing the simplified mooring system to replace the original mooring system in a scale model experiment.