CFD를 이용한 Wake Equalizing Duct의 최적설계

Abstract

In this paper, the wake equalizing duct(WED) form optimization has been carried out using computational fluid dynamics(CFD) techniques. The WED is a ring-shaped flow vane with foil-type cross-section fitted to the hull in front of the upper propeller area. The main advantage of WED is power savings resulting from the uniformity of velocity distribution on the propeller plane, reduction of flow separation at the aftbody and lift generation with a forward force component on the foil section. This study intends to evaluate these functions and to find optimized WED form for minimizing viscous resistance and equalizing wake distribution. The study uses Four parameters of WED, which are Angle of section, longitudinal location, and Angle of axis of half rings against the longitudinal and transverse planes of the ship, in the optimization process. KRISO 300K VLCC2(KVLCC2) is chosen for example ship to demonstrate WED for optimization. The optimization procedure uses genetic algorithms (GAs), a gradient-based optimizer for the refinement of the solution, and Non-dominated Sorting GA-Ⅱ(NSGA-Ⅱ) for Multiobjective Optimization. The results show that the optimized WED can reduce the viscous resistance at the expense of uniformity of wake distribution.