For a purpose of designing and developing a 2D floating breakwater model which has high performance in a wide range of frequencies, a theoretical and numerical analysis based on Boundary Element Method (BEM) for a 2D asymmetric floating body in waves is studied. An experiment is conducted to confirm correctness of the analysis method. Utilizing this analysis method, an optimization method called Genetic Algorithm (GA) is then employed to find an optimal model shape. In GA implementation, the fitness of each model, which is defined as Performance Index (PI) in this study, is measured from its reflection and transmission wave coefficients obtained by BEM. For easy remeshing, each side of the body surface is represented by Bezier curves which can be drawn conveniently by a set of control points. This set of control points represents a chromosome of an individual/model. Genetic operators of GA will modify the chromosome of each model which is then computed by BEM to obtain its fitness. In this study, it is shown that the fast computation of BEM and the ability of GA to explore a search space make the combination of GA and BEM very effective in obtaining an optimal model satisfying defined criteria.
From technical and economical points of view such as construction cost, transportability, fresh water preservation, and design flexibility, floating-type breakwaters are more preferable to be installed in a nearshore area than conventional gravity-type ones. Although many designs and concepts have been developed, the present designs for floating breakwaters are still less efficient especially when looking for higher wave-reflection performance over a wide range of wave frequencies. Accordingly, it is needed to develop an optimization scheme to determine semi-automatically the shape of a floating breakwater which has high performance in a wide range of wave frequencies.
