A novel macroscopic numerical framework for modelling wave interactions with thin porous structures

Porous structures are widely employed as an effective means of wave energy dissipation for the protection of coastal and offshore infrastructure. This study develops a novel macroscopic numerical framework, grounded in viscous flow modelling, to simulate wave interactions with thin perforated plates. In contrast to conventional microscopic approaches that explicitly resolve pore-scale geometries, the proposed model homogenises the porous zone into an equivalent continuum. A pressure-drop formulation, accounting for both viscous friction and inertial resistance, is introduced as a momentum source term to characterise flow behaviour within the equivalent porous domain. Relative to a high-fidelity pore-scale model, the framework reduces computational cost by over 90% while maintaining deviations of less than 5% in wave transmission and pressure drop. The model is validated against controlled laboratory experiments conducted at a fixed water depth of 0.5 m, with incident wave heights ranging from 0.008 m to 0.060 m. Parametric analyses reveal that increasing wave steepness ( kA = 0.0167-0.1247) enhances the reflection coefficient (from 0.155 to 0.272) and normalized pressure drop (from 0.296 to 0.632), in agreement with experimental observations. Reducing the discharge coefficient ( μ ) from 1.0 to 0.5 produces a 30% increase in pressure drop, highlighting its strong influence on energy dissipation. Increasing the normalized wavenumber ( kd = 1.0-2.6) and porosity (τ = 0.2-0.4) improves wave transmission by 19% and 33%, respectively, whereas increasing the relative plate thickness ( b / λ > 0.02) suppresses both transmission and reflection, accompanied by asymmetric pressure distributions across the plate. These results demonstrate that the proposed macroscopic framework achieves a robust balance between computational efficiency and predictive accuracy, offering a powerful tool for the design and optimisation of porous coastal and offshore structures. • Macroscopic CFD model for wave interactions with thin perforated plates is developed. • A novel pressure-drop is proposed for macroscopic CFD models. • Enhanced modelling accuracy in low wave steepness regimes is demonstrated. • Over 90% reduction in computational time was achieved compared to microscopic model. • Parametric analysis reveals the effects of porosity, wave steepness, and plate thickness on wave dampening.