Experimental Investigation of Bank Effects Under Extreme Conditions

This chapter illustrates an experiment on bank effects in extreme conditions conducted with three ship models: a tanker, a mono-hull ferry, and a catamaran ferry. The influence of propeller loading on bank effects and the wave pattern during bank passage were also studied. It was found that the sway force and the yaw moment are not always proportional to ship speed squared. A working propeller induces a suction force and a bow-away moment. In the wave systems created by the tanker and the ferry, Bernoulli wave is significantly magnified and dominant. Interaction between Bernoulli wave and wash waves was observed in the catamaran's wave system. The sway force will turn into a repulsive force when a ship is operated in extreme shallow water and close to bank in the same time. Both the sway force and the yaw moment can become surprisingly large in this case. If this occurs, a proper maneuver would be to run a small drift angle towards the bank side, while also setting a rudder angle towards the bank side. A rotating propeller induces a suction force component to the sway force and a bow-away moment component to the yaw moment. The higher the propeller loading, the larger the contribution.