Study On Dynamics And Numerical Simulation Of Aeolian Sand Morphology

The blown sand movement is formed by the sand on the ground that blown by wind. The erosion, transporting and stacking effect of the wind and sand blown by wind on the surface substances, known as the wind effect; Sand morphology formed by the wind effect, known as aeolian sand morphology. Blown sand movement and aeolian sand morphology are the most common sand movement form in the desert area, the evolution of the blown sand movement and the air flow field characteristics closely related to the substances on the sand surface. The substances on the sand surface, not only being transported and stacked by wind, but also formed a variety of ripple forms. Therefore, ripple is the most basic form of the sand morphology in the desert area. Although ripple have regular geometric patterns and generally appearance as a little ascent at the windward and the steep at the leeward, however, due to the ever-changing natural conditions, the shape of the ripples are not always orderliness. The interaction between the air flow and the different sand grains makes the external shape and internal structure of the ripples complex and diverse.Previously, researches on sand movement are mainly based on field observations and wind tunnel tests, mainly about combining the sand movement with the ripple patterns and forming process, use the fluid mechanics theory to improve the sand movement research to a complete theoretical system. With the improving of the test methods and computer technology, numerical simulation gradually become an important tool for study the mechanism of Aeolian ripple formation. Considering the diversity and complexity of the ripple, numerical simulation technologies brought great convenience on establishing the equations of sand movement, conducting the numerical simulation and comparing the calculation results and experimental data’s.In this paper, in order to study the desertification problem caused by blown sand movement, the basic theory of blown sand movement by wind is studied and the mathematical model of the blown sand movement by wind is established. Firstly, according to the fluid mechanics theory described the constitutive equations of air flow field, analyzed the relations and the independence between the air flow field and sand flow field, secondly, from the dynamic point of view analyzed the sand flow field and its establishing process in depth by considering the several keys of sand particles as saltation, creep, avalanche and suspension, and established the mathematical model of the blown sand by wind. Finally, the mathematical models of the air flow field and sand flow field are discreted. Blown sand movement is complex particle movement and it is difficult to calculate the forming process of aeolian sand morphology. Therefore, in this paper, simulations of different models under different boundary conditions of the sand ripple formation, growth, changing process and the effect of complex obstacles like desert highway and desert vegetation on the forming process of sand morphology are conducted by computer programming calculation and the simulation results are analyzed and compared with the field observations.