Volume 10, No. 3, June 2010, Pages 272-281 PDF(383 KB)
An Overview of Surface Conditions in Numerical Simulations of Dust Devils and the Consequent Near-surface Air Flow Fields
Zhaolin Gu1, Wei Wei2, Yongzhi Zhao3
1 Department of Environmental Science and Technology, School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an 710049, China
2 School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049, China
3 Zhejiang University, Hangzhou 310027, China
Dust devils are generally attributed to the near-surface conditions, usually the composite actions of the surface parameters, such as heat flux, wind shear and surface friction. Dust devil scale (DD-scale) numerical modeling has been developed to simulate the air flow of dust devils (Gu et al., 2006, 2008). In the DD-scale model, local vorticity is imposed on the boundary domain (the outer dust devil), as described by Lewellen et al. (2000). The computational domain is close to the size of convective plumes. The predicted physical parameters of Arizona-type dust devil, such as the maximum tangential velocity, the updraft velocity, the pressure drop in the inner core region and even the inverse flow at the top of the core region, approach the observation results, testifying the validity of the DD-scale modeling. The effects of buoyancy (ground temperature) and surface friction (surface momentum impact height) on the fine scale structure of dust devils are further examined in this paper. The results indicate that even with small temperature difference (weak buoyancy), severe dust devils may be formed by strong local vorticity, and that different surface momentum impact heights may result in different conic angles of corner flow.
Dust devil; Convection; Large eddy simulation (LES); Vortices; Surface friction.