Research On The Roll Motion Of Ocean Engineering Ships With Anti-roll Tank In Waves

The ship sails in the waves.When the ship’s natural period is close to the wave period,resonance will occur,which causes large roll of the ship and harm the navigation safety of the ship.In order to reduce the roll of the ship,people choose to install the anti-rolling device such as the anti-rolling tank on the ship.Therefore,it is of great practical significance to study the movement of ships with anti-rolling tanks in waves.This paper studies the roll motion of ships with anti-rolling water tanks in waves..Firstly,the natural period of the anti-rolling water tank and the law of change of the dimensionless attenuation coefficient are studied.Then,According to the natural period of the ship’s roll,the water valve switch condition of the anti-rolling tank and the height of the liquid level of the anti-rolling tank are selected,so that the ship-water tank system satisfies the principle of "double resonance".and then we carry out the model test and numerical simulation study of the ship moving in the wave with the anti-rolling tank.Firstly,the free decay model test of the anti-rolling tank was carried out.And the results of the free decay period and the dimensionless damping coefficient of the antirolling tank when different water valve switching conditions and different liquid level heights are obtained.Through experiments,it is found that closing the water valve and increasing the liquid level can increase the free decay period and the dimensionless damping coefficient of the anti-rolling tank.Then,based on the Inter FOAM solver in OpenFOAM,this paper proposes a numerical algorithm to simulate the liquid sloshing motion in the anti-rolling tank.The simulated free decay motion of the anti-rolling tank is simulated,and the free decay period and dimensionless damping coefficient of the anti-rolling tank are compared with the model test results.The results are in good agreement,which proves that the numerical simulation algorithm proposed in this paper is reasonable.We also carried out a numerical simulation study on the sloshing moment of the liquid in the anti-rolling tank when the anti-rolling tank is rolling.We have found that when the roll amplitude of the anti-rolling tank is constant,the sloshing moment of the liquid in the anti-rolling tank is the largest when the rolling period of the anti-rolling tank is equal to the natural period of the anti-rolling tank.When the roll period of the anti-rolling tank is constant,the sloshing moment of the liquid in the anti-rolling tank increases as the roll amplitude of the anti-rolling tank increases.Then,According to the results of the free decay test of the anti-rolling tank,in order to make the natural period of the anti-rolling tank as equal as possible to the natural period of the ship’s roll,this paper selects the water valve of the anti-rolling tank to be fully closed,and the liquid level of the anti-rolling tank is 0.13 m.Then we conducted a model test of a ship with anti-rolling water tanks.The results of the ship’s roll motion response with and without the anti-rolling tank at different wave periods are obtained.Finally,this paper uses a simplified algorithm to simulate the torque of the antirolling tank with the measured motion data of the ship with anti-rolling tank.Moreover,we wrote a program for solving the motion of the ship in the waves,and realized the simulation of the movement of the ship with the anti-rolling tank in the waves.The simulation results are in good agreement with the experimental results,indicating that the simulation results of the anti-rolling tank torque are reasonable.The program proposed in this paper to simulate the liquid sloshing motion in the anti-rolling tank has important theoretical significance and engineering application value for the prediction of the movement of the ship with anti-rolling water tank.