Simulation Of Freak Waves And Analysis Of Interaction Between Freak Waves And Floating Structures

Freak waves are destructive waves,with both extremely large wave height and highly transient,and can lead to damages of marine and offshore engineering equipments.At present,The theoretical equations about freak wave have limitations,and the generation mechanism and the effects factors are still unclear.The study on the freak wave is still in its infancy,due to the low probablity of occurrence of freak waves and rare measured data.There is much less research on the interaction between the freak waves and the marine floating structures.Based on CFD method,this paper carries out research on freak wave and wave-body interaction,whose main research contents are as follows:(1)Based on the hydrodynamics theory and the structural dynamics theory,the mathematical model of interaction between wave and structure is established,including the continuity equation of incompressible fluid and the N-S equation,dynamic equation of linear elastic structure after finite element discretization,and the free surface,fluid-solid interface,wall boundary,infinite far-field boundary conditions and initial conditions.(2)Based on the traditional linear wave superposition theory,the freak waves are simulated through the secondary development of Fluent(CFD software)in two-dimensional and three-dimensional numerical wave tank.The limitations of the limit-focus wave model and the feasibility of the combined waves model for simulating freak waves are analyzed.(3)Based on the method of Bi-directional fluid-solid coupling and Slicing theory,the numerical model of the interaction between the freak wave and the rigid floating structure is established in the two-dimensional numerical wave tank.The variation of the wave surface and the motion history of the structure are calculated and analyzed,which are contrasted with the relevant test results to verify the feasibility of the method in this paper.Based on this,a series of operating conditions are calculated to abtain the variation of waves around the structure,motion response,surface water level and slamming loads,analyze the mechanism of green water,and achieve the numerical simulation of the strong nonlinear process of the waves such as wave rolling,splashing etc.(4)The coupled numerical model of the interaction between the freak waves and the aluminum floating pontoon is established in the 3D numerical wave tank,and the motion response,hydrodynamic response and structural response of the pontoon under the freak waves are calculated.