Research On Motion Response Of Damaged Ships In Waves

Once the ship is damaged,it will not only endanger human life,but also cause serious damage to the marine environment.To carry out research on the coupling between the flooding water,the liquid tank sloshing and the ship movement is of theoretical,practical,and environmental significance both for the rescue and towing plan making of damaged civilian ships,or to improve the after vitality of damaged warships.In this paper,the CFD method based numerically simulations of the internal and external liquid exchange process and tank sloshing induced by the damage are carried out to investigate the damaged ship performance with(and without)speed.The main research work and results of this paper are as follows:(1)Based on viscous fluid dynamics and free surface treatment technology(VOF method),a mathematical model for the coupling movement between internal and external liquid exchange,tank sloshing and ship sway after the ship is damaged in waves is established.(2)With the STAR-CCM+ software platform,the inflow process and the movement of the liquid tank caused by the flooding water process are simulated numerically,and the time history curves of the inflow process and the movement of the liquid tank are obtained.The simulation results are compared with the existing test data to verify the correctness of the numerical calculations.Then the ITTC resistance model DTBT5415 is selected for the damaged liquid tank modelling and to establish the computational flow field.The numerical simulations of the flooding water process and motion state of the liquid tank are carried out.The numerical results are compared with the computational results of the loss of buoyancy method in ship statics theory.The results agree well with each other.(3)By using the velocity inlet wave-making method,a numerical wave tank with wave-making and wave-eliminating capablity is established.Verifications of the effectiveness of the numerical wave tank was made by comparison with theoretical results.On basis of this,the motion responses of DTBT5415 in different wave directions and damage positions are calculated respectively.The numerical simulation of liquid sloshing in the damaged tank is carried out,and the differences of the motion the damaged ship the complete ship are investigated by comparisions.It’s found that under the beam sea condition,the weather side hull damage is more dangerous compared with the lee side damage.Regardless of the incident wave direction,recognizable low-frequency components exists inthe heave motion of the damaged ship.While the pitching motion amplitude of the ship become smaller after damaged.(4)The numerical calculation of the motion responses of the damaged DTBT5415 ship with speed in waves are carried out,the change of the motion of the damaged ship relative to the complete ship under the head wave condition is analyzed,and the influence of different towing speed on the motion response of the damaged ship is studied.It is found that the sailing resistance of the damaged ship is significantly larger than that of the complete ship.The heave motion amplitude of the damaged ship with larger speed is significantly larger than that with lower speed.