Motion Prediction Of Damaged Ship Based On Roll Damping Coefficient

Ship as an important means of transportation on water,once damaged,will lead to water inflow or liquid leakage,make the ship sink and tilt,seriously affect the buoyancy and stability of the ship.Under the coupling effect of beam waves and water sloshing inside the cabin,the damaged ship will have more obvious rolling motion than the intact ship.Therefore,it is of great engineering significance to study the roll motion prediction of damaged ships in beam waves.In this thesis,the hydrodynamic force of damaged cabin is added into the differential equation of intact ship roll motion in the form of damping moment.CFD is used to simulate the forced roll motion of the damaged ship,and the additional mass and roll damping coefficient of the damaged ship are calculated.A method for predicting roll motion of damaged ship at zero speed in static water and beam waves is established,which can predict the motion quickly and effectively.Firstly,the fixed and forced rolling water flooding processes of the damaged cabin are studied.Through the establishment of physical and numerical models of damaged cabin,the model test and numerical calculation of fixed and forced rolling water flooding are carried out,and the numerical results are compared with the experimental results,which verified the accuracy of computational method of CFD numerical simulation of water flooding of damaged cabin.On this basis,numerical simulation and analysis are carried out for the resonant and non-resonant forced roll motion of the damaged cabin,as well as damaged cabin roll at the beginning of the water flooding process and damaged cabin roll at the end of the water flooding process.Secondly,the forced roll motion of 2D section and 3D intact ship and damaged ship is studied.By simulating the forced roll motion of 2D S60 hull,the roll damping coefficients with different amplitudes at the same frequency are obtained,and compared with the experimental values,the reliability of the method is verified.Thirdly,the forced roll motion of 3D DTMB 5512 intact ship and damaged ship is simulated numerically,and the reliability of numerical simulation used CFD of forced roll motion of 3D hull is verified.The roll damping coefficients of the intact ship with different amplitudes at the same frequency are calculated,and compared with the values in literature,the accuracy of the roll damping calculation method is proved.On this basis,the additional mass and damping coefficient of damaged ship under different amplitudes and frequencies are calculated,and the influence law of frequency and amplitude on the additional mass and damping coefficient is analyzed.Finally,the prediction method of roll motion of damaged ship in static water and beam wave is studied.Based on the differential equation of intact ship roll motion,the hydrodynamic force of damaged cabin is added into the equation in the form of damping moment,and the prediction program of roll free decay motion of damaged ship in static water and roll motion in beam waves is developed.The accuracy of the program is verified by simulating the roll free decay motion of intact ship and damaged ship at zero speed in static water.On the basis of the above work,the rolling motion of damaged ship in beam waves at different wavelengths is simulated numerically,and the accuracy of the program in predicting ship motion in waves is verified.