scholarly journals Reconstructing the electrical structure of dust storms from locally observed electric field data

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Huan Zhang ◽  
You-He Zhou
Keyword(s):  
Electric Field ◽  
Charge Density ◽  
Space Charge ◽  
Charge Separation ◽  
Field Data ◽  
Space Charge Density ◽  
Dust Storms ◽  
Dust Particles ◽  
Electrical Structure ◽  
Separation Mechanisms

Abstract While the electrification of dust storms is known to substantially affect the lifting and transport of dust particles, the electrical structure of dust storms and its underlying charge separation mechanisms are largely unclear. Here we present an inversion method, which is based on the Tikhonov regularization for inverting the electric field data collected in a near-ground observation array, to reconstruct the space-charge density and electric field in dust storms. After verifying the stability, robustness, and accuracy of the inversion procedure, we find that the reconstructed space-charge density exhibits a universal three-dimensional mosaic pattern of oppositely charged regions, probably due to the charge separation by turbulence. Furthermore, there are significant linear relationships between the reconstructed space-charge densities and measured PM10 dust concentrations at each measurement point, suggesting a multi-point large-scale charge equilibrium phenomenon in dust storms. These findings refine our understanding of charge separation mechanisms and particle transport in dust storms.

scholarly journals Quantifying the large-scale electrification equilibrium effects in dust storms using field observations at Qingtu Lake Observatory

2018 ◽  
Vol 18 (23) ◽  
pp. 17087-17097 ◽  
Author(s):  
Huan Zhang ◽  
Xiaojing Zheng
Keyword(s):  
Linear Regression ◽  
Ambient Temperature ◽  
Charge Density ◽  
Space Charge ◽  
Space Charge Density ◽  
Transport Processes ◽  
Dust Storms ◽  
Dust Concentration ◽  
Stationary Time Series ◽  
Dust Particles

Abstract. Dust and sand electrification, which is a ubiquitous phenomenon in dust events, has a potentially dramatic effect on dust and sand lifting and transport processes. However, the effect of such electrification is still largely unclear, mainly due to its complexity and sparse observations. Here, we conducted an extensive observational analysis involving mild and severe dust storms with minimum visibility, ranging from ∼0.09 to 0.93 km, to assess the electrical properties of airborne dust particles in dust storms. The space charge density has been estimated indirectly based on Gauss's law. Using the wavelet coherence analysis that is a method for evaluating the correlations between two non-stationary time series in the time–frequency domain, we found that the space charge density and dust concentration were significantly correlated over the 10 min timescales (on the order of the typical integral timescale of atmospheric turbulence). We further presented a simple linear regression (SLR) model to quantify such large timescale correlations and found that there was a significant linear relationship between space charge density and dust concentration at given ambient temperature and relative humidity (RH), suggesting that the estimated mean charge-to-mass ratio of dust particles was expected to remain constant (termed as the equilibrium value μ∗). In addition, the influences of ambient temperature and RH on μ∗ were evaluated by a multiple linear regression (MLR) model, showing that the μ∗ is nonlinearly related to environmental factors. The present study provides observational evidence for the environmental-dependent electrification equilibrium effects in dust storms. This finding may reduce challenges in future quantifications of dust electrification, as it is possible to exclude effects, such as the particles' collisional dynamics, on dust electrification.

scholarly journals Quantifying the large-scale electrification equilibrium effects in dust storms using field observations at Qingtu Lake Observatory

2018 ◽  
Author(s):  
Huan Zhang ◽  
Xiaojing Zheng
Keyword(s):  
Linear Regression ◽  
Ambient Temperature ◽  
Charge Density ◽  
Space Charge ◽  
Space Charge Density ◽  
Transport Processes ◽  
Dust Storms ◽  
Dust Concentration ◽  
Stationary Time Series ◽  
Dust Particles

Abstract. Dust/sand electrification, which is a ubiquitous phenomenon in dust events, has a potentially dramatic effect on dust/sand lifting and transport processes. However, the effect of such electrification is still largely unclear, mainly due to its complexity and sparse observations. Here, we conducted an extensive observational analysis involving mild and severe dust storms with minimum visibility, ranging from ~ 0.09 to 0.93 km, to assess the electrical properties of airborne dust particles in dust storms. The space charge density has been estimated indirectly based on Gauss’s law. Using the wavelet coherence analysis that is a method for evaluating the correlations between two non-stationary time series in the time-frequency domain, we found that the space charge density and dust concentration were significantly correlated over the 10 min timescales that is on the order of the typical integral time scale of atmospheric turbulence. We further presented a simple linear regression (SLR) model to quantify such large timescale correlations and found that there was a significant linear relationship between space charge density and dust concentration at given ambient temperature and relative humidity (RH), suggesting that the estimated mean charge-to-mass ratio of dust particles was expected to remain constant (termed as the equilibrium value μ*). In addition, the influences of ambient temperature and RH on μ* were evaluated by a multiple linear regression (MLR) model, showing that the μ* is nonlinearly related to environmental factors. The present study provides observational evidence for the environmental-dependent electrification equilibrium effects in dust storms. This finding may reduce challenges in future quantifications of dust electrification, as it is possible to exclude effects, such as the particles’ collisional dynamics, on dust electrification.

scholarly journals Effects of three-dimensional electric field on saltation during dust storms: An observational and numerical study

2019 ◽  
Author(s):  
Huan Zhang ◽  
You-He Zhou
Keyword(s):  
Electric Field ◽  
Field Data ◽  
Numerical Study ◽  
Three Dimensional ◽  
Vertical Component ◽  
Dust Storms ◽  
Dust Particles ◽  
Sand Transport ◽  
Dust Transport ◽  
Dust Events

Abstract. Particle tribo-electrification 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 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 mainly limited to one-dimensional (1-D) E-field. Here, we quantify the effects of real three-dimensional (3-D) E-field on saltation, through a combination of field observations and numerical modelling. The 3-D E-fields in the sub-meter layer from 0.05 to 0.7 m above the ground during a dust storm are measured at Qingtu Lake Observation Array site. The measured results show that each component of the 3-D E-field data nearly collapses on a single 3-order polynomial curve when normalized. Interestingly, the vertical component of the 3-D E-field increases with increasing height in the saltation layer during dust storms. Such 3-D E-field data close to the ground within a few centimeters has never been reported and formulated before. Using the discrete element method, we then develop a comprehensive saltation model, in which the tribo-electrification between particle-particle midair collisions is explicitly accounted for, allowing us to evaluate the tribo-electrification in saltation properly. By combining the results of measurements and modelling, we find that although the vertical component of the E-field (i.e. 1-D E-field) inhibits sand transport, 3-D E-field enhances sand transport substantially. Furthermore, the model predicts that 3-D E-field enhances the total mass flux by up to 63 %. This suggests that a truly 3-D E-field consideration is necessary if one is to explain precisely how the E-field affects saltation during dust storms. These results will further improve our understanding of particle tribo-electrification in saltation and help to provide more accurate characterizations of sand and dust transport during dust storms.

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

2020 ◽  
Vol 20 (23) ◽  
pp. 14801-14820
Author(s):  
Huan Zhang ◽  
You-He Zhou
Keyword(s):  
Electric Field ◽  
Field Data ◽  
Numerical Study ◽  
Vertical Component ◽  
Decomposition Methods ◽  
Dust Storms ◽  
Dust Particles ◽  
Sand Transport ◽  
Discrete Wavelet ◽  
Triboelectric Charging

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.

Study of the Effect of Electrophoresis on Transport of Biomolecules in Microreactors

2011 ◽  
Author(s):  
Sina Jomeh ◽  
Mina Hoorfar
Keyword(s):  
Electric Field ◽  
Charge Density ◽  
Space Charge ◽  
Stokes Equations ◽  
Surface Concentration ◽  
Space Charge Density ◽  
Uniform Electric Field ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Chemical Reaction Kinetics

The effect of electrophoresis (i.e., applying uniform electric field to use the natural charge of particles) on the transport of a sample (like biomolecules) in active microreactors is numerically investigated. Navier-Stokes equations are solved along with the equations of electrostatics, species mass transport in the buffer and chemical reaction kinetics at reactive surfaces. Unlike previous studies, in which the effect of the charge of the sample bulk on the electric field has been neglected (i.e., the assumption of electroneutrality), here space charge density is assumed to be nonzero. As a result, the governing equations become fully coupled. The efficiency of the microreactor device is analyzed for two different geometries commonly used in biomolecule separation (i.e., open channel and microcylinders). It is shown that the electroneutrality assumption can drastically influence the final adsorbed concentration depending on the device configuration. Average adsorbed surface concentration is compared for each case as a measure of the performance of the device. The plots depicting the influence of the electric field and nonzero space charge density on the bulk concentration profile and the velocity field are also presented and discussed.

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