The Coupling Mechnism Between Turbulent Wind Flow And Particle Dynamics Aeolian Sand Trnsport

Desertification and sandstorm are the severe environmental problems in northern arid and semi-arid regions, and are great concerns of the whole society. Aeolian sand transport which is primarily comprised of the saltations of a large number of sand grains near the surface under the action of wind flow is the main initiating and maintaining mechanism of the wind erosion and sandstorm. Therefore, the study of aeolian sand transport is crutial to understanding the physics of sandstorm and further to controlling the disaster. Considering the importance of the turbulence characteristics if wind flow and the wind-sand coupling, this paper sets up an equilibrium aeolian sand transport model, applying finite difference method to simulating the turbulent wind flow.The wind vertical profiles were investigated by considering sand-wind coupling in the aeolian sand transport. The outline of the main research work is as follows:1.From analyzing the research development of the mechanics mechanism of aeolian sand transport, the deficiency of the current numerical research of Aeolian sand transport is presented. Previous mathematical models of Aeolian sand transport did not consider the turbulence characteristics of wind flow and the effect of wind-sand coupling.2.Considering that the Aeolian sands is influenced by the turbulence of atmospheric boundary layer wind flow, we quantitatively analysed of of the forces acting on the sand saltating in aeolian sand transport, and set up the controlling equations of gas-solid two phase flow for aeolian sand transport.3. Based on the incompressible N-S equations closed with K-ε turbulence model which can reflect the wind turbulent properties. The wind-sand coupling is involved in the gas-solid two phase model by adding a drag term induced by the sand particle movements in the unsteady N-S momentum equation.4. steady-state Navier-Stokes momentum equations,adds the unit volume resistance against wind field by Aeolian sands, and sets up control equations of wind field.5. The controlling equations of turbulent wind field and boundary conditions are discretized with finite volume method.solves discrete equation applying SIMPLE algorithm is applied to solve the discretized equations.thus the flux profile and wind vertical profile in the aeolian sand transport are simulated.6. Aeolian sand transports for different particle sizes and different friction wind velocities are simulated. Compared the simulated results with the measured results of wind tunnel by Dong et al.the established wind-sand coupling model of aeolian sand transport is verified to be reasonable and feasible. The simulated results indicate that the turbulent characteristics of wind field and sand-wind coupling have important effects on sand massflux profile and wind vertical profile in aeolian sand transport.