| With the development of ocean field,a large number of large ships and offshore platforms emerge at the historic moment,and the operation of multiple offshore engineering structures is becoming more and more common.This large offshore floating structure is composed of multi-part modules,and there are small gaps between adjacent floating bodies.The resonance phenomenon of water bodies formed in the gaps is serious to the safety of offshore operations.Heavy hazards have gradually aroused widespread concern in engineering and academia.The resonance phenomenon of the water body in the clearance is reflected in that when the wave frequency approaches the resonance frequency of the water body in the clearance,the water body in the clearance increases substantially,which affects the wave climbing changes on the upstream side and the back side of the structure.The actual marine natural conditions are complex,and the deep-sea environment is more complex and uncertain than shallow water and medium-depth sea areas.In practice,strong non-linear waves will also be encountered when operating at sea.For example,extreme wave(also known as focused wave,freak wave),which will pose a great threat to the safety of offshore operations.Regular wave,as the basis of studying and analyzing other wave forms,has always been the focus of research work.Therefore,on the basis of studying regular waves,it is of great significance to study the effect of extreme waves on adjacent floating bodies with gaps in deep water environment.The viscous effect in the narrow gap will cause energy dissipation,and the actual wave height will be smaller than the theoretical value.Therefore,the traditional potential flow theory can not accurately predict the wave heights in the narrow gap.Based on the potential flow theory,an improved high-order boundary element method is used to carry out the nonlinear numerical model experiments to simulate the effects of extreme waves on adjacent floating bodies under regular waves and deep water conditions.Waves are generated by the method of internal wave generation,and the extreme wave is generated by the form of wave focusing.Damping layers are set at both ends of the tank to eliminate reflection and transmission of waves.Artificial damping terms are introduced into the narrow gap to equivalent viscous dissipation of water.The free surface satisfies the kinematic and dynamic boundary conditions of the fully nonlinear free surface.The hybrid Euler-Lagrangian method is used to track the particles of the instantaneous free surface fluid.Firstly,a fully nonlinear numerical model is established for the interaction of regular waves with adjacent double boxes,and the non-linear characteristics of the narrow gap water body between two boxes are mainly studied.By comparing the numerical simulation results with the experimental data,the accuracy of the numerical model is verified.Under the action of different incident wave heights,the corresponding damping coefficients and the variation law of damping coefficients with incident wave heights are determined.Then,the influence of wave nonlinearity on resonant wave heights and resonant frequencies in narrow slots is obtained through numerical experiments.The variation of wave heights on the upstream side and the back side is compared.Then,the simulation of the extreme wave acting on the fixed double box with narrow slit in deep water is studied.The accuracy of the numerical flume model is verified by comparing with the published experimental data and numerical results.Then,the wave heights at the center of the narrow gap,the weather-side and the lee-side of the wave are studied when the focus position of the wave is different.According to the variation of the damping coefficients obtained by regular waves with the incident wave heights,the changes of the resonance wave heights at the center of the narrow gap and the effects of the extreme wave on the wave heights at the weather-side and the lee-side of the wave are analyzed. |
PDF Full Text Request