Three-phase flow simulation of beach erosion induced by breaking solitary waves

A three-phase (air, water, and sediment) flow computational-fluid-dynamics model based on OpenFOAM was used in the present work to simulate the beach erosion induced by breaking solitary waves. The simulation results were first validated by comparing them against experimental measurements. The simulated time series of the surface elevation and pore pressure, as well as the simulated beach profile after erosion, compared fairly well with the experiment. The simulation results showed that the wave runup and rundown processes were accompanied by distinct hydrodynamics and sediment transport characteristics. The hydrodynamics in the runup stage is featured by a weaker flow before the wave breaking and a stronger one afterward, which then gradually weakens toward the runup limit. The hydrodynamics in the rundown stage is featured by a generally weaker flow compared to the runup stage. The flow is also stronger before the hydraulic jump and weaker afterward. A flow reversal and the exfiltration process are captured by the numerical model at the end of the rundown stage. The sediment transport in the runup stage is featured by an intense rate but a short duration, while the sediment transport in the rundown stage is much slower but has a longer duration. As a result, the total amounts of the transported sediment in the runup and rundown stages were comparable to each other. Finally, a discussion on the limitations of the numerical model and possible modifications to further improve the model in the future is presented.