Conceptual Design And Hydrodynamic Performance Research Of Assembled VLFS

Since the beginning of the 21 st century,various countries have increased their funding for the research on the utilization of marine resources,and the research on Very Large Floating Structures(VLFS),a key infrastructure for various offshore operations,is also in full swing.For the VLFS foundation,due to its large size,it is difficult to be manufactured in the dock as a whole.Using the assembled form can avoid this problem well,and has the advantages of flexible installation,multi-purpose,easy maintenance,and low cost.On the basis of fully investigating the current research progress of VLFS,this paper proposes a preliminary design scheme of a new type of hexagonal modular assembly VLFS foundation,giving the sub-modules and the overall main dimension parameters,and designing Three basic forms of standard type,ring-shaped type and triangle type are suitable for different application.At the same time,each sub-module is also provided with an external pontoon,which can increase its own buoyancy or change the hydrodynamic shape to adapt to different marine environments or applications,with high flexibility and maneuverability.First,the three new types of assembled VLFS and the common semi-submersible VLFS are modeled and analyzed for buoyancy and stability.After that,the 6 DOF transfer function RAO in the frequency domain,the statistical value of the motion response under irregular waves,and the ring-shaped and triangle wave surface rise response functions are calculated.According to the structure and force characteristics of different types of VLFS,different mooring systems are designed.Mooring performance analysis and safety assessment are carried out under the combination of wind,wave and current in the once-in-a-century sea state.The results show that all new assembled VLFS meet the requirements of the specification and have better hydrodynamic performance than the structure of the traditional semi-submersible VLFS.Among them,the ring-shaped VLFS foundation has the best stability.Compared with the semi-submersible foundation,it can meet the sea conditions once a year and once in a hundred years.Under the wave direction angles of 0?and 90?,sway,heave,roll and pitch response statistics are all reduced by more than 40%.The triangular VLFS foundation with single-point mooring and pontoons has the best wave absorbing performance.At any wave angle,the frequency-domain wave rise RAO in most areas of the tail end reduces by more than 60%.At present,assembled VLFS is still in the initial stage of research.The new concept of new hexagonal sub-module assembled VLFS structure,the design of main scale parameters and the corresponding mooring system are of great significance for further understanding and forecasting the motion mechanism and RAO response of this type of VLFS under the load of wind,wave and current,and promoting related research and industrial development.