Floating breakwaters under regular and irregular wave forcing: reflection and transmission characteristics

In the present study the hydrodynamic interaction of regular and irregular waves with floating breakwaters (FBs) in shallow and intermediate waters is examined experimentally in a large-scale facility. The experiments were conducted in the CIEM flume of the Catalonia University of Technology, Barcelona. The influence of incident wave characteristics and certain geometric characteristics, such as the width and the draught of the structure, on its efficiency is examined. Four different FBs configurations are examined: (a) single fixed FB, (b) heave motion FB, (c) single fixed FB with attached front plate (impermeable and permeable) and (d) double fixed FB. Results related to transmission, reflection, and energy dissipation of the incident (regular and irregular) waves on the structure are presented. For the single fixed FB, the efficiency of the structure is proportional to the width/wavelength and draught/water depth ratios. The single fixed FB operates in a highly reflective manner. On the other hand, the heave motion FB operates in a dissipative manner with much lower reflection. The attached plate in the front part of the FB significantly enhances the efficiency of the structure. No significant differences are observed between the impermeable and the permeable plate cases. Generally, the most efficient configuration has been the double fixed FB. However, with regard to cost-effectiveness, the configuration of the FB with the attached plate should be considered the most efficient for design purposes.