Study on the Minimization of Ship Viscous Resistance

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The present paper describes an attempt to minimize the viscous resistance of two-dimensional bodies and three-dimensional full form ships under certain design constraints. The minimization was made by means of Hooke and Jeeves' direct search method with an external penalty function. Frictional and viscous pressure resistances are calculated by integrating shear stress and pressure over the hull surface, respectively, which are obtained by the boundary layer calculations based on a higher order theory. In the case of two-dimensional bodies, the boundary layer calculations were made assuming that the boundary layer is laminar from the leading edge to the transition point and is fully turbulent downstream of the transition point. On the other hand, in the case of ship hulls the turbulent boundary layer calculations were started near the fore end. Optimum shapes were determined first for two-dimensional symmetric bodies. The optimum shapes obtained at Reynolds number of 10^6 and 10^7 are similar to a conventional wing section and a laminar wing section, respectively. Next, the optimum stern forms for conventional ship form were determined by the same manner.