The Study Of Modeling And Simulation Of Ship's Motions In Waves

The ship'S movement is a very complex process,especially in the wind and waves.All of this days,people study the performance of the ship'S movement pay much attention on the study of ship'S performance just in the motionless water.Actually, ship sails in the great waves. A lot of facts prove that a ship sailing well in the motionless watr mustn't sail well in the waves. So to study the performance of a ship sailing in the waves is very meaningful. Main word here is to study ship's motions in the waves.Based on classic 3 DOF(Degree of freedom)MMG(Ship Manoeuvring Mathematical Model)model,an equation of ship'S 6 DOF motions including surge , sway , heave , roll , pitch and yaw is established.Additional,the models of inertia force according to fluid,viscous force according to fluid,screw force and rudder force are separately formed,which realizes simulation of ship'S motions with kinds of forces working together.In the simulating system,the equation of ship'S 6DOF motion is worked out and every force model is calculated.If ship'S parameters and other sea condition parameters are set in the program.ship'S motions can be simulated.And there are some additional functions,including data information showing and curves drawing and ship'S parameters,wave'S parameters,sea conditions changing,and also including saving data.The system is a 3D simulation software;it also realizes three—dimensional display.Based on the system we have created before,simulation analysis for the motions of rolling,pitching and heaving has been done.A lot of simulating curves for the motions of rolling,pitching and heaving drawn are divided into three conditions to discuss.The first iS in the same sea condition but different wave angles,the second is in the same sea condition but different ship velocities,and the third is in the different sea conditions but the same wave angle.By a large number of curves were analyzed,a lot of laws for ship'S motions of many kinds of sea conditions are gained,which can help ship sailing safe in the waves.Such laws carl be derived from the simulation that the ship'S safe navi gation in the sea to provide some reference.