Study In Wind-Blown Sand Motion With Thermal Diffusion And Heat Convection

Concerning problems on atmosphere dynamics of thermal diffusion and thermal convection produced by the sand-bed temperature in the mechanism of wind-blown sand movement,this dissertation presents some theoretical modeling and analysis for wind-blown sand movement and the natural phenomenon of electrification with thermal diffusion and thermal convection.First threshold wind and saltating trajectory of sand are quantitatively calculated with influence of thermal diffusion;then wind-blown sand flux is simulated and some pivotal results are obtained;finally wind-blow sand motion effected by heat convection in atmosphericboundary layer is reappeared through theoretical simulation.The main achievements are made in the following aspects:1,Based on considering the sand-bed temperature,the equations on thermal diffusion and thermal convection are founded and used to simulate wind dynamics. This is the base for studying wind-blown sand motion in following chapters.2,The process is quantificationally analyzed that sand starts and saltates in space in wind field with the effluence of thermal diffusion produced by the sand-bed temperature.If the sand-bed temperature is higher,the sand threshold wind velocity is smaller and both of the maximal saltating height and span become bigger.3,A theoretical model with thermal diffusion from the sand-bed is suggested to account for the effects of both thermal diffusion and electric field produced by charged sand grains during the evolution of wind-blown sand flux,where the coupled interaction is among wind velocity(vertical and horizontal wind),sand movement and the electric field.Then the evolution of wind-blown sand flux is simulated,and some pivotal results can be obtained,such as variational electric field,the transport rate of grains and so on.4,Applying Large-Eddy-Simulaton method,the atmospheric boundary layer equations are calculated numerically with thermal diffusion and thermal convection,and sand and dust motion law is simulated in this wind field.