Wave Attenuation On Fluid Mud And Its Numerical Simulation

Waves propagating over fluid mud damp dramatically, which is usually not taken into consideration in most of the numerical wave models. Various kinds of simplified models describing the constitutive relation of fluid mud are studied in the present thesis. The wave-mud interaction layer-model is applied to calculate wave damping over fluid mud. Wave height attenuation coefficient is gained and is compared to that from the two-layer fluid Bingham model, as well as the experiment results. A method is proposed to simulate wave damping by introducing equivalent bottom friction coefficient into the numerical model. By assuming that the equivalent bottom friction coefficient is proportional to the ratio of wave height attenuation, an equivalent bottom friction coefficient is then introduced into the Boussinesq equation and the mild slope equation (MSE), respectively, and wave attenuation is simulated. The results are also compared with those of physical model. The following conclusions can be drawn.(1) Through comparing standard errors between the experiment values and the numerical values, it is found that the result by applying the constitutive relation of visco-elastic-plastic (VEP) model to layer fluid model (LFM) will be better than that by using the two-layer fluid Bingham model.(2) In general, wave damping rate will increase as fluid mud density increases and will decline when wave height increases, but will become smaller when the mud loses its fluidity.(3)When considering the effect of wave damping caused by fluid mud in the numerical model, the values from LFM should be multiplied by a factor that is greater than 1. For the data used in the present study, amplifying factor 5.44 is for BE model and 2.35 for MSE model.