Study On Ship Hydrodynamic Interaction Forces In Restricted Waters

With the continuous development of the concept of Green,Safety and Intelligence,there is an ever-increasing demand for the research on ships or ship-to-ship interaction forces in restricted waters.In particular,the influence of second-order wave loads can not be ignored.On the one hand,a simple and convenient method is needed to simulate the restricted condition,on the other hand,an effective numerical method is also needed to improve the calculation accuracy of the tangential velocity for ships with sharp corners.Therefore,in this paper,the Image Green's Function(IGF)method is used to simulate the boundary effect of the restricted waters.Meanwhile,the first-order Taylor Expansion Boundary Element Method(1st order TEBEM),which can effectively improve the computational accuracy of tangential velocity at sharp corners,is used to solve the Boundary Integral Equation(BIE).According to the different boundary constraints,the IGF that satisfies the interference is given.The influence of the image virtual ship on the real ship is numerically solved by the spatial positional transformation,and the Boundary Value Problem(BVP)under different interference conditions is given.The problems of interaction forces and moment between two ships moving on parallel tracks under meeting and overtaking conditions in shallow water are systematically studied.The numerical results,which verify the accuracy and effectiveness of the proposed method,are in good agreement with the experimental results and the other numerical results solved by constant panel method(CPM)and higher-order boundary element method(HOBEM),respectively.Meanwhile,the influences of water depth,lateral distance between two ships and the speed of two ships on the interaction forces were analyzed.Based on the complex frequency-domain Green's function that satisfies free-surface conditions,the first-order and second-order hydrodynamic problems of zero-speed structure on the side wall effects are discussed.Compared with the experimental results and the Source Method(SM)results,it is proved that TEBEM can effectively deal with hydrodynamic problems on structure with sharp corners.The virtual experiment,implemented on KVLCC2 ship model,can provide the guidance for physical experiment.The added resistance of KVLCC2 ship model at low speed was studied systematically under the influence of physical wave tank,and the interference of different speed and water depth to the motion response and added resistance was considered.It can be found that the most dominant components of added resistance also are waterline-integral term and the speed square term for low speed ship using the near-field formula.