Research On Source Terms Of Shallow-Water Spectral Wave Model Based On Physical Model Experiment

The SWAN model improved from WAM of the third-generation ocean wave model has a very wide range of applications when it comes to extrapolating wave elements in coastal areas.It can perform wave generation and propagation calculations from the laboratory to the continental shelf at sea scale.The higher accuracy of the SWAN model in the near-shore shallow water is due to the addition of depth-induced wave breaking and traid wave-wave interactions terms.Because SWAN has too many source terms in the simulation of large-scale wave generation and dissipation,it will be difficult to analyze the impact of these two sources on the simulation process.Therefore,in this paper,based on the experiments of wave propagation and breaking of shallow water slope topography,where the physical processes are simple,depth-induced wave breaking and the traid wave-wave interactions are main influences,the simulation results of the SWAN model are compared with the measured significant wave height,spectral averaged period,and wave spectrum.In-depth analysing of the impact of these two source settings on the numerical results of the SWAN model.First,based on the SWAN model,combined with the physical model experiment terrain and irregular wave incident conditions.As input to SWAN we use the experimental spectrum at wave gauge 1 as the boundary condition.Establishing a one-dimensional SWAN model that can reasonably simulate shallow wave breaking.Secondly,in this paper,the traid wave-wave interactions and depth-induced breaking items are set as the default algorithm in the SWAN model,and compared with the measured significant wave height,spectral averaged period,and wave spectrum.The comparative study find that the simulation results of significant wave height can basically reflect the increase and attenuation of wave height in the measured breaking process.The setting of breaking parameters is the key factor affecting the results.This article gives an appropriate value range when the breaking parameters are constant through analysis.The evolution of spectral averaged period and wave spectrum is mainly affected by the calculation of the traid wave-wave interactions term.However,the traid wave-wave interactions approximation algorithm of the SWAN model results in a large difference between the calculated wave spectrum type and the actual measurement,and there are phenomena such as high frequency overestimation and low frequency underestimation.This makes the calculated value of the spectral averaged period smaller.Therefore,if we want to improve the spectral averaged period of the near-shore region and the simulation accuracy of the wave spectrum,the calculation accuracy of the traid nonlinear term in the SWAN model still needs more research and improvement.In addition,this paper introduces and simulates a new shallow water crushing parameter value program,which comprehensively considers the influence of terrain slope and average wave number.Compared with the simulation results when the crushing parameter is set to a constant,the accuracy of the wave height before the surf zone is improved,but more reasonable topographical studies and verifications are still required for the reasonable value of the important parameters.Considering that the traid wave-wave interactions term in the SWAN model is the main factor affecting the wave period and spectrum simulation results,and the results are significantly different from the measured ones.Therefore,this paper compares the SWAN model with the high-order Boussinesq equation model with good nonlinearity.Then results show that the averaged periods and wave spectrums calculated by the Boussinesq equation after wave breaking are more consistent with the measured ones.The comparison of the SWAN model with the physical model and the Boussinesq equation model shows that the approximation algorithm of the traid wave-wave interactions term in the SWAN mode still needs improvement.The research in this paper can provide reference for the source item setting of SWAN model in practical application,and provide basis and direction for its future improvement work.