ABSTRACT: Aims of this work are to investigate the influence on wave energy dissipation for a π-type floating breakwater, according to nondimensional variables. The related FB dissipation coefficient distributions are examined with respect to two parameters: the first one is a geometric approximation of the wave period scaled with the heave natural motion period of the FB; the second is the wave steepness. A Monte-Carlo based error analysis is carried out in order to evaluate the amount of error propagation involved in the derivation of dissipation coefficients. Results show that the two invoked parameters appear to be the key for the description of the multiple processes here involved.
INTRODUCTION Transmission coefficient τ, defined as transmitted to incident wave heights ratio, and reflection coefficient ρ (reflected to incident wave height ratio) are considered the most important parameters to define the efficiency of floating breakwaters (FB). If we separate the radiated waves generated by the FB induced motion, we must argue that from a physical point of view, transmitted wave is what remains after the processes of reflection and dissipation. Actually, the shape of the incoming wave is first deformed due to partial reflection and possible breaking induced by the FB. The energy that is not reflected passes below and in some cases above (overtopping) the structure. In both cases some energy is dissipated. We therefore think at energy loss (dissipation) as a key point to be investigated for a whole understanding of a FB efficiency problem. The phenomena related to energy loss in passing a FB are somewhat difficult to be isolated and measured. The errors on the analysis of wave transmission and reflection, even carried out with the most efficient techniques, are brought into the above computation, leading to high uncertainties in the dissipation process.