2D water-wave interaction with permeable and impermeable slopes: Dimensional analysis and experimental overview

Abstract

The main objective of this research is to characterize and quantify the prevalent physical processes in the energy transformation of a regular wave train when it interacts with permeable and impermeable breakwaters. Two sources of experimental data are considered: (a) numerical experiments on an undefined impermeable rigid slope, using the numerical model (IH-2VOF), and (b) physical experiments on a non-overtoppable permeable breakwater with a cube armor layer and a porous core of finite width in a 2D wave flume. A revised dimensional analysis reveals that the relative water depth, h/L, and the incident wave steepness, H/L, at the toe of permeable and impermeable breakwaters are the key factors to define and optimize the experimental space (HI/L, h/L). Moreover, the product of (h/L)(HI/L) can be applied to identify the type of wave breaking and the domains of wave energy transformation, and to quantify the reflected and transmitted energy coefficients and the dissipation rate (KR2, KT2, D*). Fitting an experimental curve (i.e. a sigmoid function) to the impermeable data, the slope is a plotting parameter. The same conclusion is obtained for a permeable breakwater; in addition the wave energy coefficients depend on the relative breakwater width B*/L, and the relative core grain size and D50,p/L, and armor unit diameter, Da/L. Because the range of the design factors spans several orders of magnitude, a log-transformation provides a well behaved experimental space [ln(h/L), ln(H/L)] which is likely of benefit to verify the wave breaker type and the related dissipation-reflection-transmission on slopes. Finally, this study shows that there is not a biunivocal relationship between the Iribarren number, Ir, and the type of breaker, the reflection and transmission coefficients and the bulk dissipation. Therefore, Iribarren’s number is not a sufficient similarity parameter for the analysis of wave breaking, and related flow characteristics on slopes.