Experimental study on the dynamic response of a water ballast type floating breakwater

Abstract

Water ballast type floating breakwater has a wide range of applications due to its good wave attenuation performance. In this study, a series of physical model tests have been carried out to get insights into the dynamic response characteristics quantitatively of the floating breakwater, and tension of the mooring lines. The external and inner water pressure and its distribution on the floating body are presented. The results show that the sway and roll motions of the floating body exhibit strongly nonlinear characteristics as a result of “water-on-deck” and “sloshing” occurrence. The heave motion maintains a downward drifting and the greatest heave amplitude occurs when the wave period is close to the heave natural period. At both waveward and leeward side of the floating body, the mooring lines give almost comparable amplitudes, but opposite phase, of tension in terms of both upper and lower. The maximum water pressures appear at the waveward side, which is near the still water level. At the corner between the floating box and the vertical plate, the pressure changes sharply, leading to a “snap'' value. Overall, the results in this study provide a database for detailed design for the water ballast type floating breakwaters in future structural and material selection.