Estimation of roll related hydrodynamic coefficients through the free running model tests

When a fast container ship or a naval vessel is turning, comparable roll motions occur. Therefore the roll effect has to be considered in the horizontal equations of motion of the ship to predict the maneuverability well. In this paper, a new method to determine a model structure of hydrodynamic rolling moment acting on a ship and estimate its coefficients by applying the system identification technique to the data of sea trial tests or free running model tests has been proposed. To obtain the motion data to be applied to the proposed algorithm, the apparatus of free running model of a large container ship was developed and the standard maneuvering tests were carried out in a lake. The model structure was built in through the data of the turning circle tests and the 20-20 zig-zag test, and then confirmed through the 10-10 zig-zag test. We conclude that the model structure of hydrodynamic rolling moment can be established easily through the free running model tests without a number of captive model tests.