Empirical formula for approximating added resistance of ships in waves

What is it about?

An attempt was made to extend and further tune the existing formula for approximating the added resistance in head seas to cover a wider range of speed and to account the impact of loading conditions; a new parameter based on B/T was introduced after conducting extensive parametric study to capture the influence of draft on the added resistance; the trim effect has also been investigated; Furthermore, the draft effect on the added resistance due to diffraction is further tuned and simplified. The derived formula uses only a few input, including only some ship dimensions to yield an estimation of the added resistance of ships in regular waves. Numerical results show that the added resistance of various ships in head seas at low speeds, as well as the added resistance of tankers in ballast condition and cruise ships, can be properly captured by the new formula. Hence, it meets the demand of fast examination of the minimum power; it can also be used in the early design stage of a ship for power estimation.

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Why is it important?

There are several empirical formulas for the estimation of the added resistance in waves, but they do not account, in general, for the impact of the loading condition. Especially when the ship is in ballast condition, her draft and trim has significant effect on the estimation of the added resistance in waves. This is addressed in the present paper.

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