Some Model Experiments on Rolling Damping of a Ship in Shallow Water

Abstract

This report relates to some model experiments with respect to the shallow water effect on roll damping of a ship with forward speed. The free and forced rolling tests were carried out to obtain the roll damping coefficients. These tests were conducted by employing a tanker type ship named ESSO OSAKA. The experimental results indicate that roll damping force increases with decrement of water depth regardless of the extent of the ship speed. In addition, it can be said that rate of the increase in shallow water is grater than that in deep water. Moreover, the lift component of roll damping force in shallow water was estimated from the steady characteristics of lateral forces on the ship hull. The lateral forces were determined from oblique tow tests performed at finite water depth. There is fair correspondence between the lift component and roll damping force due to forward speed. As a result, it may be concluded that in shallow water condition the lift component occupies the major portion of roll damping caused by advance speed.