Numerical modelling of hydrodynamics of permeable pile groins using SWASH

This paper focuses on a specific form of groins, Permeable Pile Groins (PPGs), consisting of a single or double rows of wooden piles. With only few experiments and simulations available to study the hydraulic functioning of PPGs, the correlation between the effectiveness and the characteristics of the groin system has yet to be fully understood. This paper presents the application of SWASH, a non-hydrostatic wave-flow model to simulate flow fields affected by PPGs. The SWASH model was calibrated to correctly reproduce longshore current fields in the laboratory. Then, introducing PPGs in the model, the simulation results are compared with available experimental measurements to investigate current-PPG interaction. The simulation results, which generally agree well with the measurements, show that PPGs hardly attenuate wave energy but considerably retard longshore currents within the groin fields. Rip currents are predicted to develop at both flank sides of each pile groin, due to local positive water level gradients toward the pile groins.