Dynamic Interaction Between Surface Water Waves And Muddy Seabed

The dynamic interaction between waves and muddy seabed is studied. The mud is considered as a non-Newtonian fluid with complex rheological property including viscosity, elasticity, and plasticity. An extraordinarily generalized constitutive equation is proposed, which includes various existing models as special cases. The numerical method is based on the well-known SMAC method in modern CFD, but the discretization of the momentum equations is replaced by a weighted implicit scheme to achieve a better stability, which is definitely necessary when mud with very large viscosity is involved.The response of muddy seabed to surface water waves is investigated based on the non-Newtonian fluid flow model established. The wave action is represented by periodic pressure acting on the surface of the seabed. The effects of the viscosity, the elasticity, and the plasticity of the mud on the motion of the seabed and its resulting mud transport are discussed. The relationship between wave height and the amplitude of the velocity, the rate of mass transport and energy dissipation is also clarified.A fully coupled model is also developed to deal with the dynamic interaction between waves and the muddy seabed. The k-εturbulence model is used. The free water surface is treated by the VOF method, while the numerical method for tracing the moving water-mud interfaces and the interfaces between different mud layers is specially developed, which combines the essence of ENO and Youngs'reconstruction scheme. The coupled model is applied to the study of wave propagation over a mud layer under various conditions. It is demonstrated that the viscous model is fairly satisfactory for mud with low density, but the plastic feature of the mud plays an important role when the density of the mud is relatively large. The model is also employed to study the effects of the seabed stratification on wave motion. It is also shown to be applicable to problems with practical background.