The Influence of the Ship's Speed and Distance to an Arbitrarily Shaped Bank on Bank Effects

Abstract

In shallow and restricted waterways, the water displaced by a sailing ship is squeezed under and along its hull. These confinements result in increased velocities of the return flow along the hull and the induced pressure distribution on the hull causes a combination of forces and moments on the vessel. If generated because of asymmetric flow due to the presence of a bank, this combination of forces and moment is known as bank effects. A comprehensive experimental research program on bank effects has been carried out in the towing tank for maneuvers in shallow water (cooperation Flanders Hydraulics Research—Ghent University) at Flanders Hydraulics Research (FHR) in Antwerp, Belgium. The obtained data consist of more than 14,000 unique model test conditions. The relative position and distance between a ship and an arbitrarily shaped bank is ambiguous. Therefore, a definition for a dimensionless distance to the bank is introduced. In this way, the properties of a random cross section are taken into account without exaggerating the bathymetry at a distance far away from the ship or without underestimating the bank shape at close proximity to the ship. Also, a dimensionless velocity is introduced to take the influence of the water depth, forward speed, and blockage into account. The proposed mathematical model for bank effects, often described as a sway force and yaw moment, is instead decomposed in two sway forces at each perpendicular.