Hull form optimization for reduced calm-water resistance and improved vertical motion performance in irregular head waves

Abstract A high-efficiency potential-flow based ship hydrodynamic optimization tool is presented in this paper to optimize hull forms for reduced calm-water resistance and improved vertical motion performance in irregular head waves. Besides calm-water ship resistance, the significant amplitudes of heave and pitch motion response spectra in irregular head waves are determined as objective functions. To obtain a more reliable result of ship motion in waves, the three-dimensional potential flow solver by using translating and pulsating line segment source Green's function is employed to solve ship radiation and diffraction problems and further to evaluate ship vertical motion. Several deformation methods are utilized to move the control points of NURBS hull surfaces to achieve the hull form deformation. For the purpose of illustration, this optimization tool is applied to the optimization design of the prototype of DTMB 5512. The resistance and vertical motion performance of four optimal hulls in Case 2 are investigated and further verified by the RANS CFD simulations. The optimization results in two cases indicate that this optimization tool can yield optimal ships with reduced calm-water resistance and improved vertical motion performance, and a reasonable determination of feasible region can increase the possibility of obtaining such target ship.