Hydraulic performance of different non-overtopped breakwater types under 2D wave attack

The objective of this research was to develop a method to calculate the hydraulic performance resulting from the interaction of perpendicularly impinging water waves on various types of breakwater. Our study was based on data obtained from physical tests in a wave flume with irregular waves. Based on this information, it was possible to derive the complex wave reflection and transmission coefficients in terms of non-dimensional parameters representing the breakwater geometry, granular materials and incoming wave train. The overall dissipation rate caused by the structure was estimated by applying the energy conservation equation to a control volume, which included the breakwater section. The logistic sigmoid function was used to describe the variation in the modulus and phase of the reflection and transmission coefficients (as well as the energy dissipation rate). Remarkably, the sigmoid function was able to define the domain of the hydraulic performance of the most common breakwaters. It is shown that the sigmoid function depends primarily on a 2D scattering parameter Aeq/L2, where Aeq is the area of a porous medium under the mean water level and L is the wavelength, and on the relative grain size of the porous medium, Dk, where k is the wave number. The logistic sigmoid curves help to include the phase of the reflection coefficient when defining the wave regime in front of, inside, and leeward of the breakwater. Practical examples of how these results can be applied are also included.