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Lanzhou University (2022)

Investigations into Particle-bed Collision and Sediment Transport Characteristics of Aeolian Sand-flow in the Gobi Desert

张潮

Titre : Investigations into Particle-bed Collision and Sediment Transport Characteristics of Aeolian Sand-flow in the Gobi Desert

Auteur : 张潮

Grade : Doctoral Dissertation 2022

Université : Lanzhou University

Résumé partiel
Gobi areas are widespread in the north and northwest of China.The arid and windy climate characteristics of Gobi area make the aeolian sand-flow(such as sandstorm)occur frequently,which has caused great harm to the production,infrastructure,transportation,even health and life of the local people.Compared to desert,the surface of Gobi is mainly composed of gravel and crust,and the ambient wind speed in the area is stronger.As a result,the aeolian sand-flow in the Gobi has different characteristics from the desert.However,most of the researches on the basic theory of aeolian sandflow mainly focuses on the desert,and the understanding of the characteristics and mechanism of aeolian sand flow in Gobi is still very limited.During wind-blown sand,the saltation of sand particles advancing in the form of ballistic jumping is the main form of aeolian sand flow,which colliding with the bed surface and jumping forward is an important driving mechanism for the occurrence and development of aeolian sand flow.Moreover,some researches showed that there is a covering layer composed of metal oxides on the surface of sand particles on the earth and terrestrial planets.The covering layer will lead to the change of mechanical properties of particles and then affect the results of particle-bed collision,and the covering layer will fall off in the continuous collision of sand saltation,which makes the influence on aeolian sand movement more complicated.However,in the existing numerical models of sand saltation,sand particles are considered to be composed of a single substance,and the influence of overburden and its shedding process on aeolian sand flow is rarely studied.Due to the hard surface state and limited sand source environment of Gobi,the impact of particle bed collision process on the local aeolian sand flow structure is more significant.Therefore,it is necessary to carry out in-depth research on the impact of sand covering layer on sand-bed collision process in Gobi area and aeolian sand flow structure.In this paper,a new method of using chemical acid and alkali solution to dissolve sand covering layer is proposed for the first time,and the impact of covering layer on collision process is studied by collision experiments.Then,the quantitative formula between the coefficient of restitution and the covering layer mass was provided.Based on the collision experiment and the improved particle tracking image processing algorithm,the particle-bed impact splash function suitable for Gobi surface was obtained for the first time.Furthermore,the empirical formula of sand coefficient of restitution and the particle-bed collision splash function were embedded into the aeolian sand flow model.And the key physical processes in aeolian sand flow were simulated

Mots clés : Aeolian sand-flow in Gobi desert ;covering layer of sand surface ;splash function ;experiment of particle-bed collision ;numerical Simulation ;

Présentation (CNKI)

Page publiée le 16 octobre 2022