Interaction Between Regular Or Irregular Waves And Muddy Bottoms

The interaction between waves and muddy bottoms, which dominate the dynamic processes in muddy coastal area, are studied in this dissertation. Special contributions are made to a better understanding of the transformation of regular and irregular waves and the mass transport of mud. The main contents and results are as follows:1. Based on the results of previous studies, the analysis on the micro-structure of mud. and also the measured data of mud sample from Tianjin harbour, a semi-empirical rheological relation is proposed and model parameters are determined.2. The dispersion relation of linear gravity waves on a semi-infinite incompressible Voigt viscoelastic fluid is studied. Some conclusions on the attenuation of water waves propogating over mud seabeds are obtained.3. A multi-layer viscoelastic model is developed, and the boundary-value problem under linear conditions about the multi-layer model is solved. Calculated values of wavelength and damping rate of wave height are compared with measured data. It is showed that the transformation of regular waves over muddy bottoms can be successfully predicted by this model.4. The governing equations and boundary conditions about mass transport of mud are derived. Detailed calculations are made to obtain the theoretical mass transport velocity profiles under the experimental conditions. The results show better agreement between the theoretical and experimental values than all previous works.5. According to the linear summation hypothesis for irregular waves, the measured spectra at the base point can be simulated by a series of component waves. Multi-layer model is used to calculate the change of each component wave height, then the transformation of theoretical spectra of irregular waves is obtained. A lot of theoretical and experimental spectra plots and parameters of spectra are compared. It is verefied that the transformation of irregular waves can be effectively described by the above method. In addition, the attenuation properties of irregular waves can be roughly reflected by the attenuation of statistical wave heights.6. The mass transport of mud is studied theoretically and experimentlly when the muddy bottom is under the action of irregular waves. The results show that the summation of mass transport velocities due to the component waves can basically describe the mass transport properties of mud under the action of irregular waves.7. The wave height attenuation rate is calculated when wave propogates over different real seabeds. It is found that the material of bed significantlly affects the wave height attenuation. It is recommended that proper model should be taken to estimate the wave height attenuation in wave calculation.