非定常波動場に関する研究 : 横断波形解析

抄録

It is well known that when a ship moves in waves, unsteady waves are generated and the resistance acting on the ship increases as compared with its corresponding value in still water. Analysis of unsteady wave field is very important for the study on seakeeping performance of ships, because many unsteady phenomena can be made clear by knowing the characteristics of wave field. In this report, we will show some investigated results on the approximate calculation method (stationary phase method) for the unsteady wave field which is given by the linear theory. By using the method we can know about the asymptotic behavior of the unsteady waves at far field. The unsteady wave pattern analysis method developed by Ohkusu is a very effective one for the study of generated diffraction and radiation waves by ships with advance velocity in incident waves. His method is that the analytical line, so to speak the cut line of unsteady wave field, is parallel to the ship moving direction, so, it is named as a longitudinal cut method. We propose a transverse cut analysis method of unsteady wave pattern as a pair of the longitudinal cut one. Experiments to obtain the Kotchin function have been carried out, and the effectiveness of the proposed method has been confirmed.