Studies on Minimization of Wave Making Resistance Based on Rankine Source Method

Abstract

In the original Rankine source method suggested by Dawson, free surface panels are arranged by means of the stream line tracing method based on the double model flow. In the present, study, however, it is replaced by an elliptical type panel arrangement. In order to satisfy the radiation condition on the free surface, the upstream difference operators are introduced in computational domain corresponding to those panels. By employment of this new type free surface panels, more accurate results can be obtained for a practical hull form, because it becomes very easy to increase the density of panels in near field of the ship.According to this improved Rankine source method, a hull form improvement problem to minimize the wave making resistance is discussed, in which the optimization is carried out under the prescribed design constraints by means of the nonlinear programming technique. In the optimization process, a weight function is introduced to represent an improved hull surface, which can generate a new smooth hull surface by multiplying it to the offset data of the initial hull surface. Design parameters expressing this weight function can be determined from the optimization process based on the nonlinear programming technique. In this paper, SQP (Sequential Quadratic Programming) is employed as the nonlinear programming. As an example of the hull form improvement, the HTC (Hamburg Test Case) container ship is selected as the initial hull form to be improved.