Investigations Of Added Resistance And Ship Motions In Waves Based On CFD

Ship's motion in waves will affect the safety and comfort of ocean-going vessels navigating in waves and ocean platform carrying on the operation on the sea,so it's of great importance to forecast ship's motion in waves accurately.Study about added resistance of ship navigating in waves can help us optimize ship form as well as ship route to finish the same work with less energy cost.The hydrodynamic coefficients of ship which can be regard as one of ship's inherent properties is related to ship's form and speed.The hydrodynamic coefficients reflects the coupling characteristics between ship's motion and hydrodynamic and making accurate calculation of hydrodynamic coefficients is the initial condition to forecast ship's motion in waves.The sea environment is complicated when ship is sailing on ocean,most of the encountered waves are short waves and oblique waves,especially for ocean-going vessels.However,most study of ship's sea-keeping performances is about head waves,ship's navigation in oblique waves and short waves has gotten little attention.Therefore,study about ship's performances in oblique waves and short waves is of great significance for engineering application.Based on the CFD viscous flow theory,numerical wave tank is built and is used for the numerical simulation of ship's forced oscillation and ship's navigation in waves,the idiographic work is as follows:First,choosing two typical ocean-going vessels S175 and KVLCC2.To compute their hydrodynamic coefficients of S175 and KVLCC2 with speed,the numerical simulations of forced oscillation of this two vessels which have the given speed are carried out.And the hydrodynamic coefficients of S175 and KVLCC2 are obtained by analyzing the time history of hydrodynamic obtained by numerical simulation.Inspired by the physical trial of ship model which can move freely in given directions,a method that calculating ship's hydrodynamic coefficients has been proposed by simulating ship's motion in waves.To certify this method,the navigation of a KVLCC2 model which has freedom of heaving and pitching at Fn=0.142 is simulated.In addition,in order to verify the relationship between motion amplitude and hydrodynamic coefficients,the magnitude of oscillation in numerical simulation of S175 forced oscillation and KVLCC2's free motion are changed for new simulations,and the calculated results are in good agreement with the above results.Then,the simulations of S175 and KVLCC2 in long head waves are carried out.The amplitude of the ship's motions and the phase difference between motions and incoming waves are obtained.Besides,in order to study the added resistance of ship during their voyage in oblique waves,the numerical simulation of S175 with freedom of heaving and pitching is carried out.For Very Large Crude Carrier?VLCC?which has a large L_pp,it is important to study the added resistance in short waves,and the numerical simulation of KVLCC2 fixed whose motions are constrained navigating in short waves at different speed is carried out.