Study On Infragravity Waves Over A Nearshore Shoal

There are plenty of ports along the coastline of China.Most of them are well designed in terms of protection against wind-and swell-waves.However,infragravity waves with periods of 25-300s can still permeate into the harbors and consequently deteriorate the mooring conditions.Many available studies focus on the resonance induced by IG waves in harbors,but few of them concerns the effect of shoal on the spatial propagation of IG waves nearshore.The present thesis systematically studies the influence of shoal on the propagation of IG waves by using a non-hydrostatic wave model SWASH.First,the accuracies of the model in suppressing spurious free IG waves and in simulation the cross-shore evolution of waves are verified against theoretical solution and laboratory experiments,respectively.Then a two-dimensional vertical non-hydrostatic numerical wave flume is established to explore the influence of the shoal on infragravity wave evolution under different hydrological conditions.Then the infragravity wave characteristics of Macun Port are analyzed.It is demonstrated that the SWASH model can simulate the evolution of infragravity wave in shoal through theoretical verification and numerical verification.According to the simulation,the infragravity waves in the shallow beach are mainly composed of the bound waves and the free waves,and the bound waves are the main components;The energy is transformed from the wave group to bound wave.Infragravity wave component show growth equal to the equilibrium response??3?^-5?2)as was presented by Longuet-Higgins and Stewart?1962?;The triad interaction is the main factor of the infragravity wave dissipation.In different hydrological conditions,Infragravity waves have regularity in the evolution process.The existing wave conditions in Macun Port are satisfied with the requirements of the operation of the port.