A numerical study of plunging breakers in the nearshore area under the influence of wind

This study aims to understand the role of wind effects on developing plunging waves in the nearshore region. This study has three types of wind: onshore, offshore, and no wind. The Navier-Stokes Equations coupled with Large Eddy Simulation (LES) were used in this study to simulate and analyze the flow field. The Volume-of-Fluid method (VOF) has been adopted to track the air and water interface. Four numerical simulations involving solitary and regular waves are conducted and show good agreement with the laboratory experiments. After the validation, this study extensively investigates the impact of wind directions and speeds in the laboratory and field scales. Our results reveal that the onshore wind speed increases, breaking waves occur earlier, and their location shifts farther from the coastline. Besides that, higher offshore wind speed delays breaking waves and brings them closer to the coastline. In the absence of wind, waves push the airflow structure forward, accelerating vertical airflow velocity and generating airflow recirculation. Airflow separation and counterclockwise vortex patterns can be observed in onshore and offshore wind conditions. Vorticity intensity increases with higher onshore/offshore wind speeds, with vorticity in offshore wind surpassing that of onshore winds at the same wind magnitude. During breaking processes, the airflow vorticity tends to weaken, although it exhibits greater strength than water vorticity. Furthermore, Froude and Reynolds numbers exhibit significant associations with water depth, particularly within the breaking zone. Within the broader context, we present a comprehensive analysis and discussion of the intricate interactions between wind and breaking waves. • Two-phase numerical model: Simulations analyze flow under wind conditions using LES and VOF methods. • Model validation: Good agreement between numerical simulations and laboratory experiments can be confirmed. • Wind impact on waves: Higher onshore wind accelerates wave breaking, while offshore wind delays and shifts breaking points. • Airflow dynamics: Offshore wind creates stronger vorticity, surpassing onshore winds at similar speeds. • Froude and Reynolds numbers: These correlate with water depth and enhance understanding of nearshore dynamics.