Study On The Evolution Of Sand Dunes And Antidunes In Rivers And Bays

Sand dunes and antidunes are the commonly-observed morphological features in rivers and bays.Their migration and evolution cannot be ignored in the waterway transportation and the exploitation of the seabed oil and gas.So the study of sand dunes and antidunes has been the important topic of the river hydrodynamics and marina science.A two-dimensional flow and bed evolution coupled numerical model was adopted in this paper,which is comprised of three parts: hydrodynamics,sediment transport and topographic evolution.The hydrodynamic equations and the sediment transport equations were solved by ADI scheme,and the topographic evolution equation was solved by WENO scheme which was proved to be more stable than FTCS scheme.Through the verification,the numerical model has enough accuracy and reliability.The present study applies the characteristic method to give the nonlinear evolution of profile forms and the variation of propagation velocity with Froude number and bar'amplitude,which are resulted by the nonlinear characteristic of the topography equation.The effects of bed slope and bottom friction on the evolution of sand dunes and antidunes are also discussed.The presented results can be useful for helping the analysis of the relevant numerical results obtained in computer simulations.In order to study the evolution characteristics of antidunes and sandridges in the ocean,this paper selected the evolution of topography in a bay as an example.The selection of the wavelength related to the topography instability was discussed,and the topography evolution wavelength with the maximum growth rate was obtained.Based on this,the evolution of the bed was simulated and found that both the bottom friction and bottom slope have an important influence on the evolution of the antidunes instability by changing the parameters of them in the process of numerical simulation.