Restricted water effects on berthed ship – passing ship interaction

The pressure field generated by a ship moving through water imparts forces and moments on objects around it, such as ships at berth causing them to range on their moorings. In extreme cases excessive berthed ship motions have caused damage to mooring infrastructure and dangerous situations for crew and passengers. Berthed ship motions can also restrict loading and unloading procedures. In order to increase port efficiency and safety an understanding of the interaction phenomenon is essential. Many authors have studied berthed ship - passing ship interaction and several empirical and semi-empirical methods have been presented to predict the interaction forces and moments imparted on a berthed ship due to a passing ship. Most empirical methods available are only applicable for water depth to draft ratios above 1.1 and open water conditions (no lateral restrictions). Many real world berthed ship – passing ship interaction scenarios occur with water depth to draft ratios below 1.1 and in laterally restricted water. Also, most empirical and semi-empirical methods assume that the interaction forces and moments vary with the square of the passing ship speed, whereas there is some evidence that this may not always be the case. This paper presents results from physical scale model experiments of bulk carrier berthed ship – passing ship interaction in two channel widths, at two under keel clearances (UKC). The results from the physical scale model experiments were also compared to predictions using an inviscid computational fluid dynamics (CFD) model. Inviscid models have been shown by other authors to adequately predict the interaction forces and moments for open water cases above certain water depth to draft ratios. To quantify the effect of the difference in berthed ship interaction forces and moments the predicted and measured interaction forces and moments were used as input, along with a generic mooring arrangement, to time domain numerical simulation software to predict the berthed ship motions experienced by a berthed ship due to a passing ship