Study Of Wave Nonlinear Characteristics For Coral Reef Topography In Three-dimensional Conditions

The nonlinear effects attend the whole process of nearshore wave propagation which is crucial for understanding the wave dynamics.Moreover,the nonlinear characteristics of waves are also closely related to physical phenomena such as extreme waves,sediment transport and coastal deformation.Therefore,the efficient and accurate prediction of near-shore wave propagation and deformation under nonlinear effects has always been a difficult for coastal engineering,with important theoretical significance and engineering application value.This project is based on numerical simulations to investigate the nonlinear characteristics of wave fields with multidirectional distribution on common flat and gradual coastal and coral reef coastal topography,combining the effects of incident wave conditions and coastal topography.Starting from the nonlinear interactions in three-dimensional wave fields,the mechanism of inducing the nonlinear characteristics of near-shore waves is investigated.Through analysing the effects of bottom topography and incident wave conditions on the nonlinear characteristics of waves,the distribution of wave no-linear characteristics under three-dimensional coastal topography conditions is revealed.The project has improved the understanding of the nature of nonlinear waves near the coast,led to scientific conclusions that are more realistic for the real coastal environment,and provided a theoretical basis for the construction of projects carried out in these types of coastal conditions.The major findings of the study include:(1)the nearshore topographic features have a significant influence on the energy distribution of the wave field and the degree of nonlinear interaction,which can be parameterised using the topographic factor into the energy distribution equation.(2)The nonlinear characteristics of the wave field within the reef flat region are influenced by the slope of the forereef bottom and the roughness of the reef flat,which can be parameterised by the Ursell number.(3)The differences between the nonlinear characteristics of waves under the influence of different reef topographies are mainly caused by low frequency waves within the reef flat region.(4)Both the principal wave direction and the wave directional spread of the multidirectional wave field have significant influences on the evolution of wave non-linear characteristics.