Numerical Simulation Of Sand Saltation On The Windward Of Sand Dune

There are three kinds of movement of sand in the wind, including the suspension, saltation and creep. Saltation is the primary motion for sand, and it is the major reason for the formation of sand toography, especilly the sand dunes. Therefore, the saltation has always been the focus of aeolian sand research. However, most of the aeolian sand research is about the saltationon on the flat sand bed, and little research has been conducted about the saltation on the inclined sand bed. At the same time, the sand dune is the major formation of sand assemblage. So the saltation on the inclined sand bed is common in the field, and the research on it is of great theoretical and practical significance. This paper has studied the sand saltation on the windward side of sand dune, and the content consists of four parts.1. At first, the mathematic model of sand saltation on the windward of sand dune is depicted, and it includes two section. Firstly, the wind field above the windward of sand dune is got by the expriential formula in wind engineering. Then the wind field can be used to calculate the trajectory of the particle in the saltation. Secondly, the governing equation is got based on the coordinate conversion and formal research about the saltation on the sand dune.2. The mathematic model of sand saltation is used to simulate the saltation on the windward of linear sand dune. Two examples in the previous research are choosed, and numerical simulation is done about the two examples. The comparison is carried on between the simulation results and the existing data, including the field data and the simulation data. It is found that the simulation by the model in this paper is in good accordance with the existing data.3. Samely, saltation on windward side of curvilinear sand dune is also studied by the mathematic model. Sand dunes of different profile are studied, while the profiles are common in nature. Primarily, the relation between the sand ejection number and friction velocity is obtained through the decoupling the sand saltation and wind field. Then, the relation can be used to simulate the saltation on the windward. The results are conpared with the classic formula put forward by Lettau&Lettau, which is often used to calculate the sand mass flux on the inclined bed. The comparison shows well consistence.4. From the comparison, it can be concluded that given the dune profile, the incoming wind field, the bed roughness, the mathematic madel in this paper is capable of simulating the basic information of sand saltation on the windward side, including the sand transport rate and the mass flux profile. However, the sand ejection number and the separation of wind on the dune top have a significant effect on the accuracy of simulation results, and more research is needed.