Research On Dust Transport And Coherent Structure In The Atmospheric Boundary Layer

In this thesis,the large eddy simulation method is used to simulate the movement of saltation particles and suspended dust in the high Reynolds number atmospheric boundary layer.The point force model is used to simulate the saltation particles,and the passive scalar model is used to simulate the suspended particles(dust).And three different coupling modes of turbulence-saltation-particles-dust are considered:(1)pure flow field,and uniformly release dust on the surface;(2)flow field-saltation particles are two-way coupling,and uniformly release dust on the surface;(3)flow field-saltation particles are coupling,and randomly release dust on the surface.By analyzing the flow field,dust and particle concentration distribution and correlation,revealing the promotion(inhibition)effect of turbulence on the dust transport process.We found:1.There is a large scale structure of streamwise in both pure flow field and multiphase flow field coupled with saltation particles.Meanwhile,there is a large dust concentration structure in pure flow field,and a small dust concentration structure in the case of coupled saltation particles.The change trend of dust concentration structure is also different when it is coupled with saltation particles or not.In pure flow field,when the dust is uniformly released from the surface,the streamwise and spanwise scale of dust first increase and then decrease with height,but the scale changes little.When coupled with saltation particles,the dust structure scale increases first and then decreases rapidly with height near the wall,and then increases slowly again far away from the wall.The concentration structure of saltation particles decreases with the increase of vertical height.2.The correlation analysis shows that in the three cases when far away from the wall,the dust concentration is negatively correlated with the flow velocity and weakly positively correlated with the vertical velocity.Near the wall,when the two-way coupling of flow field and saltation particles results in uniform dust emission on the surface,the simulation results are consistent with the experimental observation,which proves that saltation particles have an impact on dust transport.The correlation between the concentration of saltation particles and flow field,dust concentration and saltation particle concentration also further proves the corresponding relationship between flow field,saltation particles and dust.