Multi-objective optimization method of trimaran hull form for resistance reduction and propeller intake flow improvement

Abstract

Numerical optimization of a trimaran ship hull form has been carried out through an optimization platform relies on three methods: ship geometry morphing by Free Form Deformation (FFD) approach, high-fidelity viscous Reynolds averaged Navier Stokes (RANS) simulations, and Non-dominated Sorting Genetic Algorithm III (NSGA-III) algorithm for optimization progress. Furthermore, a software connector (HEEDS MDO software) manages all the processes involved. The total resistance and propeller intake flow are the objectives of the study, which pertain the study to a multi-objective optimization problem. A surface sensitivity analysis based on an adjoint solver is performed to obtain information about more significant region of the hull. Next, a FFD parametrization technique is implemented in the important introduced region from the adjoint solver. NSGA-III is employed to optimize hull form objectives and to find corresponding optimized variables. Optimum value of the design variables was obtained by trade-off investigation of Pareto optimal designs. The optimization results show a 13.3% resistance reduction and wake coefficient improves 7.58% for the acquired hull form. Asymmetric side hull, the sharper bow shape for an inverted bow, flat bottom in the stern region, suitable side hull arrangement and its length are the modifications of the optimization process.