Numerical study of erosion and deposition of sandy beach in presence of breakwater with spill hole

This paper presents a numerical study on erosion and deposition of a sandy beach installed with a breakwater bearing spill holes, aiming to understand its performance in erosion reduction. The two-dimensional (2D) governing equations for the water-sand mixture are solved by the VOF method and other techniques. The numerical approaches are validated against experimental data for wave propagation on an impermeable beach with a breakwater, scour underneath a pipeline, scour in front of a breakwater, and erosion and deposition of a sandy beach. On these bases, numerical simulations are made for three scenarios: a sandy beach, a sandy beach with a breakwater, and a sandy beach with a breakwater with spill holes. Then, the study proceeds to a detailed investigation of the third scenario with different breakwater locations, spill hole sizes, water depths, and wave heights. The results indicate that the breakwater indeed reduces beach erosion, and the breakwater location and wave height have a pronounced influence on the erosion. The breakwater's performance in reducing beach erosion achieves a maximum at a specific size of the hole opening. It is anticipated that the understanding revealed in this study sheds light on the design and application of breakwaters.