Numerical Simulation Of Waves Near Islands And Reefs Based On WAVEWATCH Ⅲ

Yongle Atoll,located in a typhoon-prone sea area,is a typical coral atoll with complex seabed topography and sharp changes in water depth.The wave propagation law in deep water is not applicable here.Therefore,it is necessary to establish a wave propagation evolution model in the island reef area to provide wave environment parameters for marine engineering projects.WAVEWATCH III has better precision and accuracy for large-scale wave simulation.In this paper,WAVEWATCH III is used to calculate the process of wave propagation from deep water to islands and reefs.The computational terrain is divided by unstructured grids,and the grids change from dense to sparse from islands and reefs to deep seas.Compared with the calculation method of nested calculation of nearshore waves,this method only needs to perform one calculation to obtain more accurate simulation results.First,a wave evolution calculation model near islands and reefs is established using WAVEWATCH III.By changing the wind input term and dissipation term in the model,the wave evolution under normal sea conditions and during the No.22 typhoon Vamco in 2020 is simulated.By comparing with the measured data,the applicability of ST2 scheme,ST4 scheme and ST6 scheme in wave simulation in island reef area is explored.Then,on the basis of using the ST2 scheme,the high-resolution ocean current simulated by FVCOM is added to build a wave-current numerical calculation model,which simulates the wave evolution process during the No.11 typhoon Noul in 2020.The simulation results are compared to explore the influence of flow field.The results show that for the near-island reef areas,the ST2 scheme is more suitable for simulating typhoon waves,and the ST4 scheme is more suitable for normal sea conditions.The wave-current numerical model after adding ocean current improves the accuracy of typhoon wave simulation,and the average relative errors of significant wave height at the two measured points are reduced by 4.13% and 7.71%,respectively.The flow field does not affect the spatial distribution of the significant wave height,and the deeper the water depth,the larger the significant wave height.The flow field reduces the significant wave height in the target sea area,and the decrease is more obvious in the deep water area outside Yongle Atoll than in the lagoon.The deep water,reef slope,shallow reef,and lagoons near Observation Bank are affected by the flow field to different degrees.The influence of the flow field on the lagoon is significantly lower than that of other measuring points.In the outer area of Yongle Atoll,the shallower the water depth,the more affected by the current.