Analysis of Π shaped floating breakwater in oblique waves: I. Impervious rigid wave boards

This paper investigates the reflection and transmission of incident waves interacting with a long rectangular breakwater with two thin side-boards protruding vertically downward, which is for brevity referred to herein as it is shaped, by the Greek letter Π. The effect of the addition of two side-boards on the performance of a rectangular breakwater is the main aim of this study. The structure is assumed to be placed in water of uniform constant depth, and an eigenfunction expansion method was used to obtain the solution. The attached side-boards are assumed to be very thin as compared to the length of the incident wave and the beam of the breakwater. The exciting forces, added-mass and damping coefficients, responses of the structure, and the transmission coefficient were all calculated for different cases and their results were analyzed, in which different waves approaching the breakwater from any direction are considered. Comparisons between the present method and other published solutions were made to verify the results for a rectangular cross section. The numerical results were also confirmed to be accurate through the energy conservation principle. Through comparison to the rectangular one having the same mass and under-tip clearance; it was found that the proposed configuration of breakwater experiences lower exciting forces and heave damping coefficient, but other hydrodynamic coefficients are higher for the present configuration. The resulting wave transmission is lower within the range of incident wave frequency tested. Thus upon tuning the design to the incident wave field, the present configuration of the breakwater may be useful.