| With the development of marine oil and gas resources exploitation technology, the application of Floating Production Storage and Offloading(FPSO) has been more and more widely, In the same time, it developes towards tedency of large-scale, deep-water and high safety requirement. In waves, liquid in inner tanks is excited to sloshing by the motion of FPSO and cause great sloshing pressure. If the pressure is large enough, it can destroy local structure. Meanwhile, the sloshing tanks also interact with FPSO and influence its motion. It is a typical coupling problem. But in present research, for tank sloshing problem, more attention has been paid to capture sloshing free surface. For ship motion and structure strength computation problem, the liquid in tanks is always been solidified and ignored its sloshing effect. However, considering both two parts, the research on the influence of tank sloshing to motion response and structure response is still few, it needs further study. In this paper, based on three dimensional frequency domain and time domain potential flow theory,linear and weakly nonlinear theory is applied for FPSO motion problems and linear theory is applied for tank sloshing preambles. Using a new hydro-structure loading transfer method,without considering the influence of mooring system, the following researches are carried out for influence problem of tank sloshing to FPSO motion response and structure response:1) In accordance with three aspects which are prediction of ship motion and load in waves, tank sloshing, coupling of ship motion and tank sloshing, the author read a large number of domestic and foreign literatures, and make a more comprehensive summarization and overview for previous study.2) Using wave theory, potential flow theory of ship motion in waves and potential flow theory of tanks inner flow field, coupling motion equations of ship and tank sloshing are established and numerically solved. Besides, load transfer method based on hydro-structure model is described.3) Based on frequency domain potential flow theory, using Hydro STAR software,frequency domain motion response of a experimental FPSO in different wave direction and filling ratio cases is calculated. By compared with experimental result, the effectiveness of calculation method is proved and influence rules of sloshing to FPSO motion response in different filling ratio cases are analyzed.4) Utilizing time domain potential flow theory, applying weakly nonlinear theory forFPSO motion and linear theory for sloshing, using HOMER software, time domain motion response and load of FPSO in multi typical wave direction cases is calculated and influence rules of sloshing to FPSO motion and load response in different moments are analyzed,moreover, the tank sloshing pressure in different moment is discussed.5) By building structure finite element model, applying hydro-structure load transfer method, wave and sloshing loads are transferred to structure model. Using Nastran module of HOMER, FPSO structure stress is calculated. The influence rules of sloshing to FPSO global and local stress in different time are explorated. Besides, larger stress regions are analyzed and some improvement suggestions are given. |
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