Abstract
This report deals with an approximate calculation of hydrodynamic forces generated by interactions between two ships which are moving along parallel courses at the same velocity. With the assumption of the rigid free-surface and infinite water depth, the calculation method is based on the linearized thin-wing theory, using sources distributed over the center plane to represent thickness effects of two ship bodies. In the previous report, it was assumed that trailing vortices having uniform strength extend along the infinite down stream. In this report, the author improved the vortex shedding model described above, considering decay of the trailing vortices. In general, the magnitude of the decay coefficient has a significant effect on the interaction hydrodynamic force. There is good agreement between the present calculations and experimental results for the lateral force acting on the after body of the two ships. In addition, it is clarified that influence of the vortex decay on the lateral force is remarkable compared with that on the yaw moment.
