| In the wind-blown sand movement,the sand particles will carry some charges due to the frequent collision contact and rubbing with other sand particles in the sand bed and in the air.When the charged sand particles move in the air,an electrostatic field will be generated,which sis called Aeolian electric field.Due to the charges carried by a sand particle and the Aeolian electric field,an electrostatic force will act on a sand particle,which will change the trajectory equation of the sand particle,and further has an effect on the transport rate in the sand flux.But also,the Surveyor 6 and 7 of USA detected that there are glow light on Moon's surface and the strong dust storm on Mars' s surface,so the scientists infer that there exist strong electric field,which has a significant effect on the detect device performance,and the data receive.In addition,many studies indicate that the charges carried by the sand particles will attenuate the signal of the electromagnetic waves in the wireless communication,which depends on the amount of the charges and the strength of the Aeolian electric field.The amount of the charges and the strength of the Aeolian electric field are related the charges carried by the sand particles.The collision contact and the rubbing make the sand particles electrified.Therefore,we carried out our work to calculate the charges carried by the sand particles due to the collisions in the sand flux to simulate the Aeolian electric field by using particle tracking method.Firstly,we compare the compression due to two spheres in different size by using three soft collision model that is Hertz model,Thornton model and Zhou model,at different relative collision velocity.Then combining the charging model of the particles due to collision with the collision model,the amount of charges carried by the bigger sphere due to a single collision is calculated,which is also compare with the experimental results to valid the soft collision model.Based on this,we choose the collision model to calculate the charges carried by sand particle in the following simulation of the Aeolian electric field.Secondly,because we use the particle tracking method to simulate the wind sand flux and Aeolian electric field,the collisions between particles will be involved in the simulation,and thus a simulated sand bed need to be prepared before simulation,which will be time consumed in the simulation because of the huge particle number and size distribution.We simulated the sand bed by using cooling method and advanced front method.The performances of two methods are compared.Then we combine the cooling method with the GPGU technology to propose a new method to generate a simulated sand bed,by using which a simulation sand bed is simulated in which the sand particle size obeys the size distribution of sand particles in Tengger desert.Finally,by using the chosen collision model and the simulated sand bed,the evolution of the wind sand flux and further Aeolian electric field are numerically simulated based on the particle tracking method due to the initial disturbance by collisions of incident sand particles to the sand bed and blown by initial log-normal wind field.The results show that the Aeolian electric field and the charge-mass ratio of sand particles will reach dynamically stable;and the Aeolian electric field decreases with the increases of the height above the sand bed surface,and the charge-mass ratio will change sign from positive to negative with the increases of the height.The influence of friction velocity on Aeolian electric field and charge-mass ratio is positively correlated.In addition,the relative humidity of the environment also has a significant effect on wind and sand electric fields.At low relative humidity,the Aeolian electric field increases with the increase of relative humidity,but at high relative humidity,the electric field decreases with the increase of relative humidity,and the electric field reaches to the maximum at 30% to 40% of the relative humidity. |
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