Particle resuspension and dispersion by a persistent vortical column of air*

Dust devils are known to easily lift a bed of fine dust particles (of the order of microns), even in the absence of a strong mean wind. Once these dust particles are lifted off they remain suspended for a long time. Therefore dust devils are an important contributor to the dust levels in the atmosphere which in turn affects climate by scattering and absorbing solar radiation. In this context, we seek to understand the mechanisms involved in particle resuspension and dispersion by a vortical column of air. Here, our objective is to identify and quantify the fluid-particle interaction forces that contribute to a formation of a core of fine dust observed in both naturally occurring and laboratory simulated dust devils. To achieve this, we utilize a four-way coupled multiphase flow model to simulate a vortical column of air that interacts with a bed of particles lifting from the ground. The current study quantifies the particle uptake fluxes and correlates them with the local flow variables, such as turbulent velocity fluctuations and shear stresses. Results are presented and compared for different particle sizes between 10 μm and 100 μm.