Investigation Of Cloaking Phenomenon And Wave Drift Force On Mutiple Floating Bodies

The offshore strctures tend to be huger and more complicated,consisting of a large number of element bodies,with the ocean development in deep sea.Wave loads such as wave drift force is one of the important environmental loading,which has significant effects on the safety and normal operation of the marine structures.The accurate predictions of structural hydrodynamic are expected to be a significant and difficult subject due to the complicated wave interactions among floating bodies.In this paper,the cloaking phenomenon and the wave drift forces on multiple floating bodies are investigated with the couple influences among bodies taken into account.At first,the numerical model is set up based on the combition of wave interaction theory and the high order boudary element method(HOBEM)to research this hydrodynamic prbolem.Then,the validation for the present numerical model has been carried out and confirmed by a four-cylinders hydrodynamic problem.This numerical model is applied in the simulation of the wave drift forces acting on floating bodies with different configurations.And the effects of wave interactions on the wave drift force acting on multi-bodies is considered by comparing them with the resluts of the single floating body.The research about the wave-direction effects on wave drift force under different wave frquencies and different gap between ajacent bodies has also been conducted.After that,the cloaking phenomenon and the reduction of wave drift forces for a certain wave frequency have been confirmed.By analyzing the wave drift force acting on floaitng bodies,the principle of cloaking phenomenon is studied.The effects of geometrical dimensions of floating bodies on the wave drift force have been investigaed.The reduction of wave drift force by cloaking phenomenon for a certain wave frequncy has been confirmed.In order to expand the application scope of cloaking phenomenon in different wave frequencies,a genetic algorithm(GA)approach for optimization of the geometrical dimensions of floating bodies is introduced.Convergence study for the optimization program has been carried out and confirmed by a simple-function-optimization problem.Then,the geometrical dimensions of floating bodies are optimezed under different wave frequencies to minimize the scattered wave energy and the wave drift forces acting on floating bodies.In this paper,based on the combition of wave interaction theory and high order boundary element method,the hydrodynamic interactions,especially the cloaking phenomenon and the wave drift force acting on floating bodies,has been systematically investigated.It is found that the wave interactions among floating bodies can not be ignored and the effects of wave directions on the wave drift force are significant.The reduction of wave drift force acting on floating bodies by cloaking phenomenon has been confirmed.Numerical results show that the occurrence of cloaking phenomenon is due to the symmetry of the whole structure.A quasi-cloaking phenomenon has been firstly found,which can effectively reduce the wave drift force acting on floating bodies.The optimization program is set up based on genetic algorithm to expand the application scope of cloaking phenomenon in different wave frequencies.Optimized geomet rical dimensions of floating bodies to minimize the scattered wave energy and the wave drift forces acting on floating bodies in different wave frequencies have been obtained.