Study On The Coupled Analysis Method Of Semi-submersible And Hydrodynamic Model Tests

With the reducing of shallow water oil and gas resources, marine resources miningactivities have gradually entered into the deep sea. As an effective tool of deep water oil andgas resources mining, the deep water floating structure always operate in harsh seaenvironment and its dynamic responses are extremely complicated. Accurately predict thefloating structure motion responses and mooring line dynamics is very important, since itplays a significant role in the design of whole floating system. Basin model tests are themost reliable way to predict floating system dynamic characteristics. However, the modeltest of deepwater floating structures with conventional scale is very hard to be carried out,due to the limited size of basin. In order to solve the problems of deep water floatingstructures model test, the hybrid model tests was proposed, which means the truncatedmooring system was used to replace the full depth mooring system to conduct model tests. Itraises a question for the model tests: the full depth mooring system could notfull equivalently replaced by the truncated mooring system, their dynamic characteristics aredifferent, and the difference is arising with the truncated factor. It is desperately needed todo further research to hybrid model tests.This paper focused the hybrid model tests of a deep water semisubmersible operated inSouth China Sea, the major works are as follows:1、Design the truncated mooring line based on equivalent static criteria. The CatenaryMethod is used here to analyze the mooring system statics. Two full depth catenary mooringsystem operated in1000m and400m water depth are truncated at200m water depth withempirical equation and Iteration method. Comparisons of the full depth mooring system andits corresponding truncated mooring system statics show the truncated method is entirelyfeasible.2、Study on the lectotype of largely truncated mooring lines and design largely truncatedmooring line based on dynamic similar. Three different types of truncated mooring lineswith the truncated factor of5are proposed. The semisubmersible moored with truncatedmooring systems is simulated with full time domain coupled analysis. The platform motionresponses and mooring line dynamics ate obtained and compared with full system,considering various factors to determine the most suitable truncated mooring line used inmodel tests. The dynamic similar design is implented after static equivalent design of the 200m depth truncated mooring lines for1500m、1000m and400m full depth mooring line.3、Carry out truncated water model tests suppose the semisubmersible operated in1500mand1000m water depth, the platform motion responses and mooring line dynamics areobtained. The numerical extrapolation and numerical reconstruction of truncated model testsare completed in DeepC and Wadam module of SESAM software respectively. Evaluate thetruncated factor effects hybrid model tests by comparing the differences between numericalextrapolation and numerical reconstruction of three different truncated factors.4、Research on the water truncated effect on truncated mooring line dynamics, study on thehorizontal truncated and mooring line top end materials effect on largely truncated mooringline dynamics. Analyze the damping of floating system, and study on the influencing factorsof mooring induced damping...