Hull-form optimization including the effects of added resistance

Abstract

This study presents a practical, empirical-formula-based framework for bi-objective hull-form optimization that incorporates the effects of added resistance to achieve a trade-off between total resistance and speed loss under realistic sea conditions. The total resistance is decomposed into calm-water resistance, estimated using Holtrop and Mennen’s method, added resistance due to waves, predicted via the SNNM-SNU formula; and wind resistance, evaluated by Fujiwara’s method. Speed loss is determined through the resistance–thrust identity method. The hull surface is represented by surface grids and deformed using an adaptive grid deformation technique based on a set of design variables. A Non-dominated Sorting Genetic Algorithm II (NSGA-II) is employed to explore the Pareto-front solutions. The proposed framework is applied to the KVLCC2 hull form across various sea states to examine the influence of geometric constraints, wave modeling approaches, and operational conditions. Additionally, a regular wave approximation method is introduced, where a single representative wave condition is used to approximate the added resistance in irregular seas during the optimization process. This approach demonstrates reasonable accuracy when the ship’s natural encounter frequency is sufficiently distant from the spectral peak of the irregular wave spectrum, offering a computationally efficient alternative for hull-form optimization in irregular waves.