Experimental investigation on the effect of water depth on roll natural period and damping coefficient of large commercial ships in shallow water regions

Extreme drought condition has led to a low water level in rivers and consequently interrupted transportation not only for large vessels but also for the small vessels which could safely passed through the rivers in the past. To avoid grounding and provide safe transits, all possible vertical motions, specifically roll motion due to wind gust and/or rudder deflection during operation inland waterways, should be carefully considered. Natural period and damping coefficient of roll are two essential hydrodynamic parameters for the prediction of roll motion.

The aim of this study is to investigate the effect of water depth on roll natural period and damping coefficient of large commercial ships passing through different water depths. The results show that the roll natural period and damping coefficient are not significantly influenced by the change in water depth for the depth to draft ratio of greater than 2.0. However, the roll period and damping coefficient increase exponentially with the decrease of water depth for the depth to draft ratio of less than 2.0.