Mean Drift Forces on Vertical Cylindrical Bodies Placed in Front of a Breakwater

This paper presents a numerical and experimental investigation of the second-order steady horizontal and vertical drift forces acting on cylindrical bodies in regular waves. The examined bodies are either kept restrained in front of a vertical breakwater or are considered free- floating when alone in the wave field. Two principally different approaches for mean drift forces determination are described: the momentum conservation principle and the direct integration of all pressure contributions upon the instantaneous wetted surface of the bodies, whereas, for the solution of the associated diffraction and motion radiation problems, analytical and panel methodologies are applied. The hydrodynamic interaction phenomenon between the bodies and the adjacent breakwater are taken into account by using the method of images. Theoretical and numerical results, concerning the horizontal and the vertical drift forces, are presented and compared with each other. Furthermore, additional comparisons are made with experimental data obtained during an experimental campaign at French research institute for exploitation of the sea (IFREMER), in France.