Effects of 3D electric field on saltation during dust storms: an observational and numerical study

Abstract

Abstract. Particle triboelectric charging, being ubiquitous in nature and industry, potentially plays a key role in dust events, including the lifting and transport of sand and dust particles. However, the properties of the electric field (E field) and its influences on saltation during dust storms remain obscure as the high complexity of dust storms and the existing numerical studies are mainly limited to the 1D E field. Here, we quantify the effects of the real 3D E field on saltation during dust storms through a combination of field observations and numerical modelling. The 3D E fields in the sub-metre layer from 0.05 to 0.7 m above the ground during a dust storm are measured at the Qingtu Lake Observation Array site. The time-varying means of the E field series over a certain timescale are extracted by the discrete wavelet transform and ensemble empirical mode decomposition methods. The measured results show that each component of the 3D E field data roughly collapses on a single third-order polynomial curve when normalized. Such 3D E field data within a few centimetres of the ground have never been reported and formulated before. Using the discrete element method, we then develop a comprehensive saltation model in which the triboelectric charging between particle–particle midair collisions is explicitly accounted for, allowing us to evaluate the triboelectric charging in saltation during dust storms properly. By combining the results of measurements and modelling, we find that, although the vertical component of the E field (i.e. 1D E field) inhibits sand transport, the 3D E field enhances sand transport substantially. Furthermore, the model predicts that the 3D E field enhances the total mass flux and saltation height by up to 20 % and 15 %, respectively. This suggests that a 3D E field consideration is necessary if one is to explain precisely how the E field affects saltation during dust storms. These results further improve our understanding of particle triboelectric charging in saltation and help to provide more accurate characterizations of sand and dust transport during dust storms.

Large-scale structures of wall-bounded turbulence in single- and two-phase flows: advancing understanding of the atmospheric surface layer during sandstorms

“…Therefore, the electrical properties of suspended dust particles in dust storms are currently unclear, and the particles' charge-to-mass ratio is usually assumed to be a constant of ∼ ± 60 µC kg −1 in many numerical models (e.g. Schmidt et al, 1998;Zhang & Zhou, 2020a;Zheng et al, 2003); this magnitude is consistent with the measurements of (Schmidt et al, 1998). Although Williams, Nathou, Hicks, Pontikis, and Bartholomew (2009) inferred that the charge structure of dust storms may be unipolar or bipolar (if particle charging occurs primarily at the ground or in midair, respectively), they neglected the effects of turbulence, which plays an important role in particle charging (e.g.…”

Circular polarization in atmospheric aerosols

“…There are additional interesting features to note. While it has been known that electrical fields are present during dust emission and play a role in the amount of dust lifted (Esposito et al, 2016;Kok and Renno, 2008;Zhang and Zhou, 2020), non-background electrical fields are also found in dust clouds at significant distance from the sources such as dust reaching Greece and the UK (Daskalopoulou et al, 2021;Harrison et al, 2018). These studies suggested triboelectrification (i.e., friction between particles) as mechanism for generation of an electric field within the cloud during transit.…”

Characterization of Wind‐Blown Sand With Near‐Wall Motions and Turbulence: From Grain‐Scale Distributions to Sediment Transport

“…However, as the main objective of this study is to eliminate the dependence of the initial motion parameters on the empirical or semi-empirical results obtained by experiments and theories, we ignore this process as in most of the previous studies (Anderson & Haff, 1991;Kok & Renno, 2009). In addition, considering the relatively small wind speed and uniform sand used in our wind tunnel scale simulation, the effects of electrostatic forces on particle motion are neglected (Kok & Renno, 2008;Zheng et al, 2003;Zhang & Zhou, 2020). The motion equation of a point-particle model mainly considers the action of drag and gravitational forces, which can be described as (Vinkovic et al, 2006;Wang & Squires, 1996;Yamamoto et al, 2001):…”