Objectives  This study seeks to optimize the total resistance and seakeeping performance of ships sailing in waves by adding appendages and changing their size.

  Methods  First, numerical calculations are performed on a KCS ship with two anti-pitching fins and a stern flap, and both kinds of appendage separately, to study the effects of the appendages on the hull. Second, thirty KCS ships with deformed appendages are obtained by changing the width of the anti-pitch fins and the length of the stern flap. The in-house viscous flow solver naoe-FOAM-SJTU is used for the calculations. Third, a Kriging surrogate model is established and applied to a multi-objective genetic algorithm to obtain the Pareto front of the hull with optimal appendages. Three KCS ships with optimal appendages are selected from the Pareto front for further analysis.

  Results  By adding appendages to a KCS ship, the pitch magnitude and average total resistance in an encounter period are reduced by about 12.7% and 12.5% respectively.

  Conclusions  The resistance and pitch magnitude of a KCS ship in head waves can be optimized by adding appendages such as anti-pitch fins and stern flaps, and changing their principal dimensions.