The development of yacht form trends toward more displacement and higher speed, so the optimization of such a yacht is an urgent need. In this paper, a semi-planing yacht, characterized by its small length-to-beam ratio, is chosen as the optimization target to reduce resistance based on simulation; and the optimization effect is verified through tests. The optimization process is as follows: firstly, obtaining the initial hull form through research, constraining displacement, local scales, and other arrangement-related parameters. Secondly, several local hull parameters are extracted and used to establish a parametric model based on Lackenby transformation, as well as a parametric modeling method based on local hull parameters. Thirdly, the comprehensive influence of different hull parameters on drag is analyzed based on numerical simulation. Finally, comparing the simulation and test results verifies the optimization and the accuracy of the simulation.
Owing to the more and more requirements on yacht such as seakeeping, structural strength, general arrangement and economy, the form design of yacht is developing towards balancing the speed and its adverse factors like small length-beam ratio, high block coefficient, which makes the FrΔ (volumetric froude number, (equation)) of a yacht at design speed has a high probability between 1.0 and 3.0 (semi-planing regime). Semi-planing is a type of ship regime between displacement and planning. During this regime, a new component of drag, spray drag gradually arises alongside spray flow, occupying a proportion that cannot be ignored as speed increases. When a ship is in the planning regime, it always maintains a specific range of proportion (Savitsky et al. 2007). However, in the transitional semi-planing regime, the proportion of spray drag remains ambiguous, primarily due to the unclear dominance of either hydrodynamic or hydrostatic forces acting upon the ship. This uncertainty in the resistance mechanism further complicates the optimization for drag reduction on semi-planing yachts, presenting a challenge for researchers seeking to enhance the performance of these vessels.
