Numerical Prediction Of Hydrodynamic Forces On A Ship In Oblique Motion With Large Drift Angle In Shallow Water

As a typical ship maneuvering motion,oblique motion is a very common state of ship sailing.In practical operation,when a ship maneuvers,sails along channel bank,sails close to another ship in parallel course,or is acted by wind,waves and current and so on,the hull will turn into oblique motion.Therefore,accurately grasping the hydrodynamic characteristic of a ship in oblique motion is very important for the prediction of ship maneuverability.In this thesis,taking the tanker KVLCC2 model as the study object,numerical simulation of the viscous flow around the ship in oblique motion in deep and shallow water is carried out by solving the steady RANS equation based on the polyhedral mesh in the CFD software STAR-CCM+.The SST k-? turbulence model is employed to close the RANS equation.For deep water conditions,the analysis of gird independence and the verification of the validity of the numerical method are executed first,then the hydrodynamic force and squat of the model at drift angles of 0~180° are predicted.For shallow water conditions,the control variable method is adopted first to study the size of the computational domain to determine the side width and the aft longitudinal length of the computational domain that are suitable for simulating the cases of large drift angle in shallow water.Then the hydrodynamic force and squat of the model at drift angles of 0~180° at different water depths are predicted,and the influence of speed on the hydrodynamic force and squat of the hull are analyzed.The validity of the numerical method for shallow water case is verified by comparing the numerical results with the current load factors of a VLCC in literature.The results show that the numerical method adopted in this thesis can effectively predict the hydrodynamic force on a ship in oblique motion with large drift angle at different water depths.The obtained tendencies of the longitudinal force coefficient,the lateral force coefficient,the yaw moment coefficient and the squat changing with the drift angle,the water depth and the speed will help better understand the hydrodynamic characteristic of ships at different drift angles and water depths.It also provides some references for adjusting the navigation state of ships and selecting the working position of tugboats.