Experimental Study on the Hydrodynamic Performance of Floating Pontoon Type Breakwater With Skirt Walls

Abstract

Floating breakwaters (FBWs) are widely used in moderate wave climatic conditions for coastal protection against erosion and for wave reduction around offshore loading terminals and open ocean construction sites. Literature shows that the width of a pontoon-type FBW is about 50% of the incident wavelength in order to achieve 50% wave height reduction at the lee side of the FBW. Hence, for a typical wavelength of 40 m, the width needed for pontoon FBW is about 20 m. Such an FBW may not be cost competitive. Is it possible to reduce the width of the pontoon FBW significantly by adding skirt walls (single, twin, triple, or five) at its keel. What will be the effect on mooring forces? In order to find solutions for these problems, experimental investigations were carried out on a typical pontoon-type FBW as well as pontoon with skirt walls. Both opaque and porous skirt walls were used. Wave transmission, reflection, and mooring forces, both on the sea side and lee side, were measured. It was found from this study that it is possible to reduce the width by 20 to 40% by introducing three or five skirt walls. However, introducing skirt walls increased the mooring forces by 10 to 30%. The results of this study are expected to be useful for cost-effective design of FBWs.