Study On The Nearshore Evolution Of Regular Waves And Their Interaction With Structures Under Wind Action

In the marine environment,the study of wind waves is usually inseparable from wind field when they propagate from deep water to shallow water.The law of wave propagation with the action of wind is more complex than that of pure wind wave or swell in coastal regions.In practical applications,the offshore buildings are generally not only affected directly by the waves,but also influenced by the interaction between wind and wave,which will result in the change of wave loading on offshore structures.It is believed that the study on the interaction mechanism between wind and various coastal dynamic factors,as well as the influence of wind on nearshore wave propagation,deformation and hydrodynamic characteristics of protective structures,is of great significance in terms of providing important reference for accurate prediction of hydrodynamic elements,design of coastal engineering,and formation of disaster prevention and mitigation standards.This paper specialized in the study of the nearshore evolution of regular waves and their interaction with structures under wind action based on the physical experiments in wind wave tank.The 2nd Stokes wave was adopted in the experiment.Two situations have been taken into account in the study while carrying out the physical experiments,i.e.,slope beach with no buildings and submerged breakwater.In the first situation,the free surface elevations,flow velocity and maximum runup of the nearshore wave under wind action were recorded and observed on the slope of 1:10 and 1:20,corresponding with plunging and spilling.In the second situation,only the 1:10 slope was used for the arrangement of submerged breakwater.The free surface deformation and wave force on the submerged breakwater were recorded and observed.Besides,on the basis of incompressible Navier-Stokes equation,a corresponding 2D numerical model was constructed based on the solver Waves2FOAM in OpenFOAM.The VOF method with artificial compression was used to capture the interface between air and water,and large-eddy simulation(LES)was used to calculate the turbulent flow.The comparison between the measured and the calculated results indicated that the numerical model could predict well the associated hydrodynamic characteristics of nearshore wave and wave load on the submerged breakwater regardless of the presence of wind.In view of the first situation,the investigation was conducted taking into account the effects of wind speed,incident wave height and slope on the hydrodynamic characteristics such as the wave breaking,flow field,turbulence and eddy.The experimental and numerical results showed that under the same wind speed coverage constraint,he smaller the surf similarity ?0 is,the higher the dispersion degree of wave breaking locations would be,and the breaker index of Hb/hb increases with wind speed under the same incident wave height.Likewise,the presence of wind would induce the increase of undertow intensity,the aggravation of turbulence and the acceleration of vortex diffusion.Depending on the breaker type,the results could be different in different situations.With respect to the second situation,the effects of wind speed,incident wave height and water depth on the hydrodynamic characteristics were investigated,including the wave load,flow field,turbulence and vortex around submerged breakwater.It has been found that the wave force load increases with wind speed,and when the wind-induced waves break near or in front of the breakwater,there will be a certain degree of attenuation.Meanwhile,the dimensionless(?)increases with wind speed,and can be utilized to characterize the wave load.Moreover,the presence of wind will enhance the transmission process of wave and weaken the dissipation process on submerged breakwater.And the undertow and turbulence intensity in front of the submerged breakwater tend to increase with the wind speed,and the range of vortex diffusion extends towards the offshore direction.Finally,based on the experimental data and theoretical analysis,the empirical formulas accounting for perdicting the wave set-up and run-up were proposed.In summary,this study aims to shed light on the wind-wave interaction mechanisms with and without buildings.Building on physical experiments,the research was conducted in connection with numerical methods to explore the nearshore evolution of regular waves and their interaction with structures under wind action.