Study on Bow Shape Optimization of Ultra Large Block Coefficient Ship and CFD Simulations of Initial and Optimized Hull Forms

摘要

The present paper describes a hull form improvement of innovative low-speed Ultra Large Block coefficient Ship (ULBS). A hull form optimization method for reducing wave-making resistance and wave-breaking at the bow using nonlinear programming method (NLP) based on the Rankine source method is discussed. In the optimization process, wave-making resistance coefficient, surface integrals of the square of free surface elevations and free surface disturbance function D(x,y) -values are selected as the objective functions. Bow-body shape is optimized under the prescribed design constraints based on the present method. Numerical examples are given for unconventional ULBS. The three improved hull forms for the corresponding objective functions are obtained by optimal designs which indicate that the objective functions are reduced distinctly. In order to verify the present optimization method based on the potential solver, the flow characteristics around the initial and bow optimized hull forms are analyzed by using Computational Fluid Dynamics (CFD) analysis based on the Navier-Stokes (NS) solver. Comparisons of the computed resistance coefficients, pressure and velocity distributions of the initial and bow optimized hull forms are presented. It is confirmed that simulation results based on the viscous flow solver show reasonable agreements with the numerical results based on the Rankine source method for the bow optimized hull forms.