Wave reflection, transmission and spectral changes at permeable low-crested structures

Physical model tests were carried out in order to improve the understanding about the hydrodynamic processes that take place around a LCS when it is under wave attack. In particular, the wave transmission and reflection coefficients as well as the spectrum transformation were analysed for both emerged and submerged structures. The results of the experiments indicated that there is a clear inverse proportionality between the transmission (Kt) and reflection (Kr) coefficients and the wave steepness sop. This trend is much more noticeable for emerged than for submerged structures. A comparison with some widely employed formulae was also made; in most of the cases these expressions underpredicted Kt and overpredicted Kr. Moreover, the spectral changes in the waves transmitted through the structure were analyzed, showing a shift of energy to higher frequency bands greater than that observed in previous works. It was also noted that the higher the sop, the more likely it is for the transmitted energy to be retained in the lower frequency bands.