Abstract: The analytical solution to the wave diffraction of compound structure of a circular cylinder circumscribed arc-shaped breakwater is derived using the eigenfunction expansion approach based on the theory of small-amplitude wave diffraction. Accordingly, the wave loads on the structure and the diffracted wave free surfaces are calculated. The calculation evaluating results show that the circumscribed arc-shaped breakwater, compared with single cylinder, could obviously reduce the direct wave loads on cylinder and the wave runup around the surface of cylinder. The structure with solid or porous outer breakwater and porous inner cylinder could get good wave prevention effect. The variations of porous coefficient of structure, incident wave angle, outer breakwater central angle, outer breakwater radius and water depth ratio, water depth and wave length ratio have influence on diffracted wave effects.

Key words: wave diffraction, eigenfunction expansion approach, compound porous structure of a circular cylinder circumscribed arc-shaped breakwater, wave force, diffracted wave free surface, wave runup