[A-OS15] Physical Oceanography (General)

[AOS15-P08] A numerical study of plunging breakers in the nearshore area under the influence of wind

*Nhat Minh Truong¹, Tso-Ren Wu^1,2,3, Chia-Ren Chu², Chung-Ye Wang² (1.Graduate Institute of Hydrological and Oceanic Sciences, National Central University, Taiwan, 2.Department of Civil Engineering, National Central University, Taoyuan, Taiwan, 3.Earthquake-Disaster & Risk Evaluation and Management Center, National Central University, Taoyuan, Taiwan)

Keywords:plunging waves, breaking waves, wind effects, internal-source wavemaker, sponge layer, LES

This study aims to understand the impact of wind on the development of plunging waves in the nearshore region, with a focus on surfing waves. This study considers three wind conditions: onshore, offshore, and no wind. This study uses the Navier-Stokes Equation associated with Large Eddy Simulation (LES) to simulate and analyze the flow field. The Volume-of-Fluid function (VOF) has been adopted to track the air and water interface. The numerical experiments are deployed and validated with laboratory experiments. The internal-source wavemaker and sponge-layer methods were used in the numerical simulations to create incident waves and absorb reflected waves. The validation involves examining the shoaling process under the absence of wind and onshore wind conditions. The numerical results agree with the experimental records of the altimeter and velocity time series. Having completed the verification process, this study explores the influence of wind direction on nearshore breaking waves at both laboratory and field scales. Besides, numerical dyes were added to track the water and bedload movement process in the surf zone to understand the impact of wind in the near-bed of breaking waves in the up-going wave. Numerical results indicate that the breaking point occurs later in offshore winds, and its effect on the seabed is greater than that of breaking waves under other wind conditions. Regarding the field-scale simulations, plunging waves run along the sloping walls under wind effects. The numerical results indicate that a steep slope results in a wave-breaking point closer to the shoreline. Detailed analysis and discussions are presented in the context.