Abstract
An analysis of experimental data from ship model tests, as published by different authors, suggests that the resistance increase in regular head waves may be represented by an analytic expression, which is sufficiently valid for cargo ships with a fine hull form. An attempt is made to derive such an expression suited for the approximate calculation of this added resistance. The formulae obtained, which may be considered as empiric, contain but one factor, (dependent upon the ship’s form) which should be evaluated by means of experiment. The present method makes it possible to calculate the resistance increase in regular head waves of any length and at any speed, provided that experimental results for merely one speed, or even for one specified wave length and corresponding (synchronous) speed are available. Moreover, by adopting an average value of the above mentioned factor, the added resistance can be calculated without any help of model experiments.
Hence, the resistance increase in irregular head waves can be calculated as well, and, as an example, the results regarding an existing container ship are given and compared with actual full-scale data.
Furthermore, the added resistance in any irregular head sea represented by a standard spectrum can be predicted very quickly by means of the enclosed graphs, which reproduce the numerical results of an adapted analytical treatment.
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