An approximative method for the determination of the hydrodynamic coefficients of a ship in case of swaying and yawing on shallow water

Abstract

This report gives information about the hydrodynamic coefficients of a box-shaped ship with zero speed of advance in case of pure swaying and yawing on shallow water. In the horizontal plane a harmonically oscillating motion is imposed on the ship; the hydrodynamic coefficients for the modes of motion of the ship are determined from the exciting forces in a theoretical as well as In an experimental way. The analytical approach is based on an excisting theory for wave generators adapted to the present case; use lS made of the strip theory. The experiments are carried out in the form of forced pure sway and forced pure yaw tests with zero speed of advance. The theoretical and experimental results for the hydrodynamic coefficients are compared with one another. It is found that the system ship-fluid for swaying can be considered as linear in case of small oscillations, at least for the frequency range examined. In case of very small oscillations for yawing the system ship-fluid may also be considered as linear. Application of the strip theory with neglect of viscous effects l s adequate for swaying on shallow water in case of small/moderate to high frequencies. In the frequency range considered the strip theory lS not satisfactory for yawing on shallow water.