Dynamics of Cage Floating Breakwater

Abstract

Floating breakwaters have potential applications in protecting minor ports and harbors such as fisheries and recreational harbors, where-in stringent tranquillity requirements are not warranted. In field applications of the existing floating breakwaters, limitations are imposed due to their large relative width (ratio between breakwater width and wave length) requirements to achieve desirable tranquillity level. This relative width requirement is greater than 0.3 for the existing floating breakwaters. To overcome the above drawback associated with the existing system a new configuration for a floating breakwater is derived, which could yield the desired performance with minimum relative width requirement. The floating breakwater comprises of two pontoons rigidly connected together and each of the pontoons having a row of cylinders attached beneath, for improved performance characteristics. The laboratory tests were conducted in both regular and random wave flumes to study the dynamic behavior of the breakwater. Transmission and reflection coefficients, water surface elevations and velocities inside the cage like area provided in between the pontoons, rigid body motions floating breakwater and mooring forces were studied under regular and random waves and under the regular waves followed by a uniform current. The results proved the suitability of the floating breakwater to the field conditions even for large wave periods. In addition the variations in water particle kinematics, rigid body motion and mooring forces show nominal magnitudes when compared to the existing systems indicating the rigidness of the breakwater.