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Lanzhou University (2021)

Study on Charges Carried by Individual Sand Particles in Field Wind-blown Sand Flux

刘亚奎

Titre : Study on Charges Carried by Individual Sand Particles in Field Wind-blown Sand Flux

Auteur : 刘亚奎

Grade : Doctoral Dissertation 2021

Université : Lanzhou University

Résumé partiel
Due to sand movement blown by wind,different aeolian landforms and sandstorms were developed,which result in desert expansion and desertification as well as environment pollution and negative impact on human beings’ physical and mental health.It had been known for a long time that the moving sands may carry a set number of charges to form aeolian electric field.When a charged sand particle is acted upon by an electrostatic force,the threshold friction wind speed is reduced ;further the sand trajectory in the wind will be changed,and thus the sand transport rate will be also affected.Moreover,charged sand particles also enhance the attenuation of electromagnetic waves when prorogating through the dust system.Therefore,the study of the amount of charges carried by individual sand particles can be helpful to quantitatively figure out the effect of the charges carried by individual sand on the threshold friction wind speed and sand transport rate ;evaluate the attenuation degree of electromagnetic wave signal caused by charged sand particles ;estimate the effect of the charges carried by individual sand particle on geomorphic evolution,and global climate change ;to understand the electrification mechanism of sand particles.Therefore,the experimental studies on the amount of charges carried by individual sand particles,especially the individual sands in filed wind-blown sand flux are conducted out.The main results are as follows.First of all,considering the aeolian electric field,an experimental study is conducted to investigate the charges carried by individual sand particles directly lofted up into air by electrostatics force in this thesis.The sand samples were placed on the surface of simulated dune under electric field.With the increase of electric field,the sand particles are lofted up from the surface,and the trajectories of the sand particles are recorded by high-speed camera.By analyzing the movement trajectory of sand particles in electric field,the amount of charges carried by individual sands are reversely calculated.There is a critical electric field,beyond which the sand particles can be directly lofted by electrostatics force.Meanwhile,the experimental results show that the higher the relative humidity of the environment is,the lower the critical electric field is.The empirical formula of the charges carried by individual sand particles lofted away from sand bed is proposed.

Mots clés : Wind-blown sand flux ;charges carried by individual sand particles ;aeolian electric field ;charging model ;field measurement ;

Présentation (CNKI)

Page publiée le 18 février 2022