Numerical Simulation of Dust Lifting within Dust Devils—Simulation of an Intense Vortex

Abstract

Abstract Based on an advanced dust devil–scale large-eddy simulation (LES) model, the atmosphere flow of a modeled dust devil in a quasi–steady state was first simulated to illustrate the characteristics of the gas phase field in the mature stage, including the prediction of the lower pressure and higher temperature in the vortex core. The dust-lifting physics is examined in two aspects. Through the experimental data analysis, it is verified again that the horizontal swirling wind can only make solid particles saltate along the ground surface. Based on a Lagrangian reference frame, the tracks of dust grains with different density (material) and diameter are calculated to show the effect of dust particles entrained by the vertical swirling wind field. The movement of solid particles depends on the interactions between the aloft dust particles and the airflow field of dust devils, in which the drag and the centrifugal force component on the horizontal plane are the key force components. There is the trend of the fine dust grains rising along the inner helical tracks while the large dust grains are lifting along the outer helical tracks and then descending beyond the corner region, resulting in the impact between different-sized dust grains in the swirling atmospheric flow. This trend will make the dust stratification, developing a top small-sized grain domain and a bottom large-sized grain domain in dust devils.