Solitary wave attenuation by vegetation patches

Abstract

The effect of vegetation patchiness on solitary wave propagation, attenuation and wave-induced forces is studied both experimentally and numerically. Vegetation patchiness is simulated with rigid cylinder configurations built by one, eight and four patches tested under emergent, near emergent and submerged conditions. These configurations are parameterized by means of a new parameter (equivalent length, Le), which is used to relate cylinders distribution with wave attenuation capacity. This new parameter allows comparing results for the three patches configurations. Larger attenuation rates are found for higher wave heights and shorter wave periods. The influence of water depth is also considered by means of the submergence ratio (SR) in order to account for the percentage of water column affected by vegetation. Higher attenuation rates are obtained for emergent conditions. High correlations are found between wave attenuation and a new set of parameters, the depth wave number (kLe × SR), that accounts for submergence conditions and field characteristics and a new Reynolds number ( R e s L e ), that is calculated considering the field vegetation dimensions affecting the flow. Experimental results are extended using IHFOAM, a three dimensional Navier-Stokes equations solver, to analyze wave forces on individual cylinders and wave propagation patterns showing the variability of forces magnitude and direction associated to vegetation patchiness.