Approximation of the added resistance of ships with small draft or in ballast condition by empirical formula

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