Catamaran Bow Hull Rapid Optimization Loop Development Using CAESES and StarCCM+

Abstract

Ship hull optimization is an iterative process, usually performed by Computer Aided Design (CAD) and Computational Fluid Dynamics (CFD) by simulating the hull form hydrodynamic performance. Researchers have been working on CAD and CFD methods to accelerate the preliminary design to make it more efficient. CAESES is a typical CAD-CFD integration platform that will be used to manage the entire optimization process. Firstly, Lackenby method and Free-Form Deformation method was implemented to a catamaran demi-hull. The demi-hull bow hull area was modified by the change of the center of buoyancy with the displacement staying constant. Then the bulbous bow was modified in length, bulb girth and the angle between the bulbous bow and the base line. By coupling the CFD solver StarCCM+ with CAESES, the wave making resistance and wave pattern of the demi-hull in calm water was simulated and optimized by Non-dominated Sorting Genetic Algorithm (NSGA)-Ⅱ. Finally, after getting the optimal demi-hull, the distance between the two demi-hull was optimized. Inviscid fluid model in RANS method was used to reduce the computing time while ensuring the accuracy in the simulations. Results show that this optimization loop can be used to reduce the wave making resistance of catamaran in calm water.

최근 개인용전산기의 발전된 계산 속도로 인해 선형 최적화에 CFD를 적용하는 연구가 많이 이루어지고 있다. 그리고 CAD와 CFD, 그리고 최적화 과정까지 하나의 통합프로그램으로 구현하여 효율성을 높인 프로그램들도 발표되고있다. CASES도 이러한 프로그램으로, 전형적인 CAD-CFD integration platform 이다. 본 논문에서는 CASES를 이용하여 쌍동선의 선형을 최적화 하고자 하였다. 선형을 변환시키는 방법으로는 Lackenby method 와 Free-Form Deformation method를 사용하였다. 쌍동선 demi-hull의 선수부분 형상을 변화시키기 위해배수량을 변화시키지 않고 LCB를 변화시키는 Lackenby method를 사용하였고,bulbous bow의 형상을 바꾸기 위해 Free-Form Deformation method를 적용하였으며, 길이, Bulb girth 길이, Bulb와 기선과의 사이 각도 등을 파라메터로 선택하였다. CFD-Solver로는 StarCCM+을 사용하였으며, 최적화 기법으로는 Non-dominated Sorting Genetic Algorithm (NSGA)-Ⅱ를 적용하였다.얻어진 최적 demi-hull 선형을 이용하여 쌍동선의 두 개의 demi-hull 간격도 최적화 하였다.