ABSTRACT
A trimaran usually consists of a main hull and two side hulls which has already been an important type of high-performance vessels. In order to reduce its total drag at different speeds for the need of saving energy and reducing pollution, the hull form optimization solver OPTShip-SJTU is used, and the spacing of side hulls and the shape parameters of the main hull can be changed and regarded as optimization design variables. Furthermore, the total drag of the trimaran is evaluated based on the potential flow theory after verifying the reliability of the potential-flowbased NMShip-SJTU solver. After evaluations of new sample hulls created by Optimal Latin Hypercube Sampling method, Kriging surrogate models are then constructed and validated to save the computational cost. Finally, a multi-objective optimization program is implemented to obtain the optimal hulls, and the selected typical optimal trimarans are further analyzed to ensure the optimization effects.
Apart from catamaran, trimaran has become one of the most growing high-performance ships in these days due to their good performances including stability, resistance and seakeeping. In the early stage of the trimaran design, the resistance performance should be considered at first in order to meet the demand of Energy Efficient Design Index (EEDI) and the urgent need for saving energy.
The total drag of trimaran is mainly determined by the hull shape and spacings of the main and side hulls. Since the main dimensions of the main hull are bigger than the those of the side hull, the shape of the main hull affects the total drag of trimaran to a larger extent, while the spacings including lateral spacing and longitudinal spacing of the side hulls relative to the main hull has a great impact on the wave interference between the demihulls. Therefore, in order to optimize the total dag of the trimaran, both the shape of the main hull and the two spacings should be considered.
