Non-uniform Sediment Transport And Sand-wave Movement Characteristics

The movement of sand waves is a significant form of bed load motion and plays an important role in the process of suspended sediment movement. As we all know, sediment in the bed moves as teams that are described as sand wave. So this kind of sediment-motion has a great influence on the flow and sediment conditions and there is a big difference in the sediment movement of the flat-bed. Obviously, sand waves have an important effect on erosion and deposition of the riverbed, evolution, structure and so on. Until now, the study on sand-wave movement is not enough and results of most researches are only a brief description of the process of the sand wave movement. Some researches about the relationship between sand waves and sediment discharge simply consider the shape of the sand wave as regular form for simple mechanical analysis. Now, there is some controversy on the mechanism of the development of sand ripple and there is no uniform standards on the stages of sand waves. The study on the relationship between the exchanges of riverbed sediment movement and sediment move can barely be discovered in today’s scientific community. Therefore, the study of sandwave movement is meaningful for perfecting the mechanism of the starting and the transport of sediment.In this research light-weight plastic sand is considered as an experimental subject in the one hundred meters water tunnel. Under different levels of flow intensity, we have collected shape parameters, observed the details of sediment motion and have made the analysis of size distribution and relative density along the water tunnel. Then, we select the important effect factors in the process of sediment transport and the factors are the basement of the research. Having made some analysis on original data, the mechanical model of sand ripple development is structured. The function of sediment motion on exchange, selection, layering, size distribution, erosion, deposit of bed-sand are researched.The results of this research show that the development of sand ripple is the outcome of regular exchange of water and sand’s energy. On the surface of sand-waves, active sand particles, especially the separation point and the meeting point are the important factors for the exchange and selection of sand particles. Along with the difference of flow intensity, the parameter of sand wave also changes regularly. Besides, the exchange of sand particles causes a phenomenon that the average particle size and relative density is increasing with increase of depth. In the end, the ultimate form of sand-wave is sand dunes or deep pools which get involved in the development of bed. The equation of sand wave movement speed is concluded and the sediment transport rate formula is improved.