Experimental Investigation On The Hydrodynamic Characteristics Of Flexible Multi-buoy Breakwater

In this thesis, the hydrodynamic characteristics of a flexible multi-buoy breakwater are investigated extensively through model tests. Two configurations for the multi-buoy were applied in the current study, one is gapless and the other is with specific clearance between the neibouring buoys. The experimental results reveal that the dissipating performance, motion response and mooring force of the floating breakwater were subjected to the relative width, relative height, relative spacing and structure pattern, etc. Based on the analyzed results, the following conclusions are drawn:(1) Basically, the flexible multi-buoy breakwater can achieve the identical dissipating performance to the twin-pontoons and other more complicated polygon twin-bodies. The wave transmission coefficient of 0.4-0.5 were measured as the width of the breakwater was 0.3?0.5 times of the wave length. Compering to other breakwaters, the flexible multi-buoy breakwater is simpler and easy to be fabricated and installed. Therefore, it is worth to recommend for engineering application.(2) The configuration with specific clearance between the buoys provided significant effect on the wave dissipating for short wave, i.e. B/L>0.8. However, this effect eliminated with the increment of the wave length, i.e. B/L?0.8.(3) The sway of the flexible multi-buoy breakwater is complicate. The spectra of the seaward force and sway showed singificant dual-peak characteristics. The scattering induced by the flexible multi-buoy breakwater is small and can be ignored.(4) The mooring tensions of the flexible multi-buoys breakwater is mainly controlled by the relative wave height. The critical seaward force was obtained as the width of the breakwater was 0.6-0.7 times of the wave length. Further increasing on the width would not lead to larger mooring tension. Comparing to the gapless configuration, the maximum mooring tensions on the gap-type breakwater could be up to 1.3?1.4 times. The leeward force is 30% less than the seaward force for both the gap-type and gapless breakwater.(5) When the width of the floating breakwater is 0.5 times of the incident wavelength, Mooring force is about 60% that of the 0.7 times of the incident wavelength (extreme value).(6) In engineering design, the width of the breakwater is usually no more than half of the wavelength. Under the same wave conditions, mooring force of the gapless configuration is smaller and hence is recommended for engineering application.