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Lanzhou University (2021)

On the Spatio-Temporal Evolution of Dust Storms:Theoretical and Numerical Modelling


Titre : On the Spatio-Temporal Evolution of Dust Storms:Theoretical and Numerical Modelling

Auteur : 张旸玥

Grade : Doctoral Dissertation 2021

Université : Lanzhou University

Résumé partiel
Dust storms are extreme weather events that usually occur in arid and semi-arid regions.Dust particles suspended in the air can greatly affect the hydrological cycle,ecological system,air quality,human health,and agriculture.A systematic and comprehensive investigation of the spatio-temporal evolution and the underlying physical mechanism is of great importance for predicting and controlling dust storms.The downburst outflow which gives rise to local convective sandstorms is essentially a gravity current.A volume of air cooled by the evaporation and sublimation of precipitation in the cloud descends and collides with the earth’s surface,spreading longitudinally in the ambient.Over arid ground,large amounts of aerosols carried by the strong wind can form a dust wall at the leading edge of the gravity current,which is referred to as a convective dust storm.On one hand,the existing CFD(computational fluid dynamics)analysis of the convective dust storms is rare and limited to coarse grids.Thus,the impact of the turbulent motions on the spatiotemporal evolution of local convective dust storms is unclear.On the other hand,the modelling of the downburst outflow lacks a sophisticated theory and an appropriate scaling approach,and barely concerns the front features.The atmospheric boundary layer is a high Reynolds number wall turbulence,which is the basic flow of regional dust storms.The main characteristics of the high Reynolds number atmospheric boundary layer are large-and very-large-scale motions,and the effect of the related coherent structures on the spatio-temporal evolution of the regional dust storm is scarcely studied.Therefore,based on the basic governing equations for incompressible flows and the Eulerian representation for dust concentration,through theoretical and numerical approaches,we develop models that can track the spatio-temporal evolution of the dust storm and the relevant turbulent flow.Theoretical models for the gravity current are improved for a suitable description of the downburst outflow.Utilizing DNS(direct numerical simulations)and LES(large-eddy simulations)can capture the complex turbulent structures and the spatio-temporal distribution of dust concentration

Mots clés : dust storms ;dust transport ;gravity current ;downburst outflow ;high Reynolds number atmospheric boundary layer ;direct numerical simulation(DNS) ;large eddy simulation(LES) ;

Présentation (CNKI)

Page publiée le 19 février 2022