短波長域における船首形状と抵抗増加の関係

抄録

The authors calculated the added resistance in short wave length by the ray theory and compared it with many experimental results by using the model with several bow forms. Ray theory explained well these results (in case of head wave and oblique wave conditions) and made the effect of the horizontal bow forms on added resistance clear. In this paper authors propose the easy method to estimate the added resistance and the mutual relation between the added resistance and the horizontal bow form in regular short waves and short-crested irregular waves. At first step, the F.P. point and shoulder point of the horizontal bow form are connected by straight line. As the result the bow form is divided into two parts. One is the rectangular part, other is the swollen part. Under zero speed condition, the added resistance acting on the bow can be separated into two components, the rectangular part component and swollen part component. The value of the rectangular component is obtained analytically and that of the swollen part component is simplified by neglecting the higher order value. Approximated formula of the forward speed effect component is proposed based on the many calculated results by the ray theory. The total values of three components are the added resistance. In case of the short-crested irregular waves, the simplified estimated method of the mean added resistance is proposed based on the method mentioned above and using the approximated wave spectrum. The proposal method could be effective on initial disign stage of a ship when a designer wants to know the effect of bow form on added resistance. The behavior of wave motion near the bow corresponds to added resistance strongly. To know the feature of unsteady wave breaking near the bow and unsteady wave patterns, an experiments to take the photo of wave behaviors near the bow are carried out and compared with the theoretical results.