Hydrodynamic Model For A Connected Multi-body Array With Arbitrary Arrangement

Based on the three-dimensional potential flow theory and the high-order boundary element method,a multi-body array model connected by hinges with arbitrary arrangement is established in the frequency domain.The motion response of the multi-body array is carried out by using a Fast Multipole Method(FMM),which can reduce the storage requirement and computation time from O(N)to O(NlogN).The complex offshore floating engineering structures such as wave or photovoltaic power generation device and floating platform are regarded as a multi-floating body array system with hinge connections.Based on the setting,the motion equation and hydrodynamic model for a mult-body array system with complex connections arranged in an arbitrary shape are established.Different from the single body hydrodynamic calculation,the calculation of multi-body array system should not only consider the coupling between waves and floating bodies,but also consider the coupling between floating bodies on the whole system.A Fast Multipole Method is applied to solve the the problem of huge computation and storage in the hydrodynamic coupling of multiple floating bodies.Different from the linear arrangement system with the end-to end connection,the multi-body array has no limitation on the size and number of bodies,and the arrangement of connecting devices can be more complex.Due to the large number of rigid bodies,it is necessary to unify the coordinate system and convert the motion equation of the known monomer in its own coordinate system into the motion equation of the array in the global coordinate system.Based on the constraint conditions of continuous displacement and equal rotation angle at the hinge joint and the force analysis of the two connected bodies,the constraint matrix under different hinge connection is derived in detail,and the hydrodynamic analysis model of multi-body array with arbitrary arrangement is established.The interaction between wave and two square boxes with rigid,hinged connection,whose result has been published by other authors,is calculated by using the mult-body hydrodynamic calculation program WAFDUT in frequency domain to verify the correctness of this method.The comparison results are in good agreement.The established numerical model is used to compare the motion response of the multi-body array system under different arrangement,connection mode,water depth and wave incident direction.