Study On The Hydrodynamic Characteristics Of A Large Floating Structure

As a comprehensive support base at sea,large floating structures provide new ways for people to solve the problems of material transfer and safety of personnel and vessels.Unlike ships and other floating bodies,large floating structures can be hundreds of meters or even thousands of meters in length.The working environment of large floating structures is relatively harsh,the characteristics of motion response are very complex.The hydrodynamic perforance will directly affect their safety and reliability.Therefore,accurate prediction of hydrodynamic characteristics of structures in waves is of great significance for the design and safety assessment of floating structures.In this paper,combining with numerical calculation and model test,the hydrodynamic characteristics of a new kind of large floating structures are discussed,which can provide basis for the optimum of structure.In this paper,the roll decay of DTMB5415 ship in still water is numerically simulated and validated based on the RANS(Reynolds-Averaged Navier-Stokes)method,and the acquisition of viscous damping is discussed according to the numerical results.At the same time,potential flow theory method is used to calculate and analyze the motion response of a box with and without viscous damping,validations are conducted by comparing the calculated results with the experimental results.Then,the viscous damping of a large floating structure is obtained by the above verified method.Based on this,the hydrodynamic performances in frequency domain and time domain are calculated,analyzed and validated by using the three-dimensional potential flow theory method.It is found that there are wave reflection and interference phenomena inside the buoy,and the water oscillation at the junction is the most obvious.The influences of gravity center,connector size and working state of structure on the hydrodynamic performance of floating body in frequency domain are discussed.The influence of wave angle,significant wave height and period on the hydrodynamic performance of floating body with mooring system in time domain are also discussed.The results show that the change of the length of the connectors between the floating bodies has a relatively large influence on the pitching and rolling motion in the peak area.The change of the center of gravity has little effect on the hydrodynamic performance of the floating body,and the hydrodynamic performance of the floating body is less affected by the berthing state,while affected by the state of buoy gate significantly.Finally,model tests are designed and conducted for the large floating structure,and the effects of wavelength and wave height on the motion response,mooring force and internal wave height of the floating body are summarized.The design scheme and test method in the model test can provide reference for the hydrodynamic research of the large floating structure or other similar research.