Study On The Hydrodynamic Characteristics Of Two Side-by-side Ships In Waves

In recent years,a kind of multi-floating offshore base built with semi-submersible vessels is proposed for the development of offshore bases which can be used under deep sea conditions.The coupling of wave motion,motions of floating bodies and responses of mooring systems may induce resonance,which may cause a large change for the free surface between the floating bodies and cause significant motion response for the floating bodies.Therefore,accurate prediction of hydrodynamic interference for multi-floatings has become one of the hotspots for ship engineering.The purpose of this paper is to find a numerical method for the prediction of hydrodynamic interference between two floating bodies side-by-side in waves.Firstly,the parallel system of Wigley ship and rectangular barge is taken as the research object.The hydrodynamic disturbance characteristics of two parallel barges in waves are numerically simulated using the methods based on solving the RANS(Reynolds-Averaged Navier-Stokes)equation,the potential flow method without considering viscous correction and the potential flow method with viscous correction.The validity of each numerical method is verified by comparing and analyzing the numerical results and experimental results.On this basis,the applicable scope of each method is summarized.Then,considering the potential flow method of viscous correction,this paper discusses the influence of ship's stern spacing and wave direction angle on the viscous correction coefficient.The results show that the ship's stern spacing and wave direction angle have less influence on the viscous correction coefficient in a certain range.In addition,the influence of the bow spacing and the wave direction angle on the mechanical characteristics of the two adjacent ships is further discussed.Finally,DTMB5415 and a semi-submersible ship(two-ship system)side-by-side are discussed.The results of the RANS method and the potential flow method with different viscosity correction coefficients are compared to obtain an appropriate viscosity correction coefficient.Then,the responses and forces of two-ship system in frequency domain are calculated and discussed.It is found that the mutual interference between the two ships is more severe in the middle and low frequency areas.Based on the frequency domain calculations,the time domain response of the two-ship system with mooring system(ship-ship-mooring system)is further studied.The motion response,cable tension and fender pressure of the ship-ship-mooring system are predicted.The influence of mooring modes and wave angles on the hydrodynamic performance of ship-ship-mooring system are discussed.The results show that the method for the prediction of hydrodynamics of ship-ship-mooring system is reasonable,which can provide references for the building of multi-floating offshore base that constructed by the semi-submersible ship.