Shape Optimization System of Bottom Structure of Ship Incorporating Individual Mesh Subdivision and Multi-Point Constraint

A structural optimization system using the Finite Element Method (FEM) for the initial design stage of a ship is presented in this paper. A general bulk carrier is selected as the object for the optimization. Some dimensions determining the shapes of the ship's bottom structure are taken as design variables. Since the design variables affect the shape of the structure, the FEM model needs to be updated during the optimization. Further, the structure of the ship is so large and complicated that optimizing the shape of the ship's structure is very difficult. The individual mesh subdivision technique and the multi-point constraint method are introduced to make this optimization possible. However, creating the FEM datasets for the ship's structure requires a lot of manpower. To remove this drawback, Prime Ship-Hull is used because it has a function for recognizing the ship's structural members. The FEM dataset which can be applied to the individual mesh subdivision technique and the multi-point constraint method is made automatically from the structural members categorized by Prime Ship-Hull. Five key design variables for shape optimization of the ship's bottom structure-height and width of the double bottom, height of the bilge hopper tank, and the 2 widths of the lower stool-are considered here. A numerical example shows that the proposed method makes it possible to optimize the shape of the ship's bottom structure.