In open and unrestricted waters the water displaced by a forward sailing vessel can travel without major obstruction underneath and along the ship. In restricted and shallow sailing conditions, the displaced water is squeezed between the hull and the bottom and/or the bank. This results in higher flow velocities and as a consequence a pressure drop around the same hull. In the vicinity of a bank this pressure drop generates a combination of forces and moments on the vessel, known as bank effects. The major achievement of the presented research is the development of a realistic and robust formulation for these bank effects. This knowledge is acquired with an extensive literature study on one hand and with dedicated model tests carried out in different towing tanks on the other. The majority of the utilised model tests were carried out in the shallow water towing tank at Flanders Hydraulics Research in Antwerp, Belgium. The data set on bank effects consists of more than 8 000 unique model test setups (which is by far the most elaborate research ever carried out on this subject). These model tests provide the input for the analysis of bank effects and the creation of the mathematical model. Overall the magnitude of the bank induced forces increase with: A higher forward speed of the ship A higher propeller load A lower under keel clearance A more confined navigation area: steeper banks, smaller channel width A smaller distance between ship and bank The mathematical model copes with a wide range of ship types and bank configurations and is suitable for implementation (and has been implemented) in full mission bridge simulators which can be used for training purposes as well as for research to support the admittance policy or exploitation of ports and waterways. |
