Evaluation of the reflection coefficient in wave absorbers with double permeable walls: flat and V-Type fronts

Purpose This paper aims to evaluate and compare the wave reflection performance of two double–permeable–wall absorbers differing only in front geometry: a flat wall and a V-shaped wall. This study seeks to quantify how front geometry influences the reflection coefficient (KR) under different wave conditions while maintaining constant porous-medium parameters, thereby identifying configurations that enhance wave energy dissipation in coastal protection structures. Design/methodology/approach Three-dimensional CFD simulations were conducted in OpenFOAM using the interIsoFoam solver to model fluid–porous–structure interaction. Both absorber geometries were analyzed under six regular wave conditions, varying wave period. Porous walls were represented through Darcy–Forchheimer formulations with constant permeability and porosity. Free-surface elevation data were extracted using ParaView and Python; the signals were then postprocessed in MATLAB, and the reflection coefficient was computed using the Mansard and Funke three-point wave separation method. Findings The results of this study indicate that the V-shaped front consistently achieves lower reflection coefficients than the flat front under all analyzed conditions. The improvement is attributed to enhanced flow deflection, fragmentation and dissipation of wave energy. However, as the wave period increases, the V-shape advantage decreases, with both configurations converging toward similar KR values. Velocity and vorticity field analysis revealed stronger and more persistent vortical structures in the flat-wall configuration. Originality/value This study provides a novel comparative assessment of double–porous–wall absorbers with identical porous properties but distinct geometries in three dimensions. The findings of this study highlight the importance of geometric design in optimizing passive wave absorbers and demonstrate that V-shaped configurations can improve energy dissipation efficiency, guiding future developments of coastal protection structures.