Ship Maneuvering, Including the Effects of Transient Motions,

In the traditional approach to the problems of ship maneuvering, on uses a set of linearized equations of motion that excludes the possibility that the hydrodynamic forces and moments might be affected by the history of the motion. Using ideas introduced by Cummins, one can obtain another linearized set of the equations of motion which contains a memory function as well as the added mass and damping coefficients. These stability coefficients have been evaluated by an impulse-response techniques, a method that is new to ship maneuvering problems and that appears to represent a substantial improvement over the traditional regular-oscillatory-motion tests. Results from both experimental methods are presented for comparison. To examine the effect of the memory function upon predictions of standard ship maneuvers, predictions of a few standard maneuvers have been calculated using both sets of the linearized equations of motion. The differences between the predicted motions were found to be small for all the cases we examined. Author