Bank effect
Bank suction and bow cushion in a confined channel, why they turn a ship toward the near bank, and their role in canal groundings.
Bank effect is the hydrodynamic interaction between a ship hull and the side of a confined channel. Water accelerating through the narrowed gap between hull and bank lowers the pressure there, so the stern is drawn toward the bank while a high-pressure region at the bow pushes the bow away from it. The net result is a yawing moment toward the far side and a lateral pull toward the near one.
The effect grows sharply with speed, with proximity to the bank and with the blockage ratio, which is the fraction of the channel cross-section the hull occupies. In a prismatic canal section with a large modern hull, bank effect combines with squat and with windage to produce a handling problem that has no equivalent in open water.
The full article will cover the mechanism and the governing parameters, the interaction with squat and under-keel clearance, the speed and clearance rules canal authorities impose because of it, its role in canal grounding investigations, and the handling technique for recovering from it.