Hull surface modification for ship resistance performance optimization based on delaunay triangulation

Author(s): 
Xide Cheng, Baiwei Feng, Zuyuan Liu, Haichao Chang (Wuhan University of Technology)

CHALLENGE - The hull surface modification method plays a vital role in ship hydrodynamic performance optimization, and should meet the following requirements:in order to save optimization time, hull surface modification should be achieved using few design parameters; the modification range of the hull form should be sufficiently large; the local modified hull surface should have a fairing connection with other parts of the hull surface; the optimal hull form should be suitable for applying to manufacturing.

SOLUTION - The RBF interpolation method is applied in order to realise ship hull surface deformation. The hydrostatical properties of each new ship, such as displacement and longitudinal position of the buoyancy centre, are calculated. If the constraint conditions are satisfied, the wave-making resistance calculation is carried out by CFD software. Otherwise, variables are modified again in order to create a new hull form. The genetic algorithm (NSGA-Ⅱ) employed in modeFRONTIER is used to drive the entire optimization process. If the maximum generation is reached, the optimal ship is output; else, the design variables are modified in order to repeat the above process.

BENEFITS - In order to validate the hull form optimization results, resistance tests were conducted on the Series 60 initial model and optimal model.​ Under conditions of free heave and trim, the total resistance of the S60-opti decreases within the entire speed ranges. Below the design speed (V < 1.49 m/s), the decreased total resistance range is small. The drag reduction effect is 8.79% at design speed. As the speed increases, the optimization effect is more obvious and reaches approximately 12%.