Electrostatic Field Model Research Articles

Study of droplet formation in parallel flow focusing microchannel under electrostatic field control

To achieve efficient preparation of emulsion droplet, this paper uses a two-dimensional mathematical model coupled with the phase field model and the electrostatic field model to calculate the droplet formation in parallel flow focusing multichannel, and analyzed the effect of electric field strength on the droplet formation process. In addition, the effects of different capillary numbers and dispersed phase viscosity on droplet formation were also analyzed. The results show that the emulsion in the channel always generates droplet by dripping regime, and the droplet have the best monodispersity. Applying appropriate electric field strength can realize droplet formation frequency and size regulation. Increasing the dispersed phase viscosity increases the breakup thread of the dispersed phase fluid, and the droplet size obtained gradually decreases, the difference in droplet size can be slowed down by applying the electric field. Increasing the electrostatic force leads to a higher droplet deformation rate. The droplet shape classification is plotted using the capillary number (Ca) and electrostatic number (CaE). It is found that the droplet flow pattern in the channel remains a circle only when Ca and CaE are sufficiently small.

Interaction mechanism of okra (Abelmoschus esculentus L.) seed protein and flavonoids: Fluorescent and 3D-QSAR studies

The binding capacity of 10 flavonoids with okra seed protein (OSP) was studied by fluorescence spectroscopy. The structure of flavonoids had an obvious impact on binding performance. The binding ability of flavanone was lower than that of flavone, isoflavone and dihydrochalcone. The binding capacity of flavonoid glycoside was superior to that of the corresponding flavonoid aglycone. The binding ability was positively correlated with the number of phenolic hydroxyl groups on the B ring. The steric field and electrostatic field model constructed by 3D-QSAR method could well explain the above interaction behavior. Thermodynamic analysis suggested that the quenching mechanism of OSP caused by flavonoids was static quenching, and the binding-site number was 1. In addition, hydrogen bonding and van der Waals force dominated this interaction. The 3D and synchronous fluorescence spectra showed that there was no significant change in the polarity of the environment around tryptophan and tyrosine residues during binding.

Method for the measurement of triboelectric charge transfer at solid–liquid interface

Triboelectrification between a liquid and a solid is a common phenomenon in our daily life and industry. Triboelectric charges generated at liquid/solid interfaces have effects on energy harvesting, triboelectrification-based sensing, interfacial corrosion, wear, lubrication, etc. Knowing the amount of triboelectric charge transfer is very useful for studying the mechanism and controlling these phenomena, in which an accurate method is absolutely necessary to measure the triboelectric charge generated at the solid—liquid interface. Herein, we established a method for measuring the charge transfer between different solids and liquids. An equipment based on the Faraday cup measurement was developed, and the leakage ratio (rl) was quantified through simulation based on an electrostatic field model. Typical experiments were conducted to validate the reliability of the method. This work provides an effective method for charge measurement in triboelectrification research.

Electric Field Distribution of Soluble Salt Deposition on the Surface of Insulators in Railway Overhead Lines

Different constituents of soluble salts have different effects on the insulation performance of insulators. To study the electric field distribution of soluble salt deposition on the surface of high-speed railway insulators, a two-dimensional model of the cantilever insulator electrostatic field and constant-current field with soluble salt deposition is constructed. The simulation results indicate that the relative dielectric constant of dry pollution is the main factor that affects the electric field distribution on the surface of the insulator. The electric field intensity is arranged in the following order: CaSO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> >KNO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> >NaNO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> >K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> SO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> >NaCl>MgSO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> , and the conductivity of each dirty liquid in the wet state becomes a key factor affecting the electric field distribution, which is specifically shown as sodium chloride>nitrate>sulfate. The simulation results are compared with existing test results to verify that they were correct. It is also found that the electric field intensity of the insulator with good hydrophobicity is slightly greater than that of the insulator without hydrophobicity. The results provide a theoretical basis for the classification of regional pollution levels and the testing of insulator contamination in the laboratory.

Parameters design of voltage sharing components for the series multi‐break mechanical switch

Series multi-break mechanical switch is one of the critical components of high-voltage hybrid DC circuit breakers. However, due to the existence of distributed capacitance, the voltage distribution between the breaks is not balanced. This paper proposed a voltage sharing configuration method of the mechanical switch of hybrid DC circuit breaker, and carried out the static DC voltage and the transient voltage distribution characteristics tests to verify its effectiveness. Considering the influence of whole structure of the circuit breaker, this paper established the electrostatic field model and circuit simulation model of a typical ±535-kV hybrid DC circuit breaker. And it analyzed the influence of single break's opening fault, breaking open distance, and the shielding fitting on the voltage distribution characteristics of series six break mechanical switch. According to the simulation results based on the Zhangbei voltage source converter-based high-voltage direct current project type test parameters, the parameters design of the voltage sharing components of the mechanical switch are obtained, which can meet the voltage sharing coefficient requirement of 95%.

Numerical investigation of electrostatic effect on particle behavior in a 90 degrees bend

Particle behavior in a turbulent circular-sectioned 90° bend under electrostatic field at three air flow rates (1600 L/min, 1100 L/min and 950 L/min, the corresponding bulk Reynolds numbers are 58,000, 40,000, 34,000) is simulated by a Large Eddy Simulation-Lagrangian particle tracking technique (LES-LPT) method coupled with electrostatic field model by Coulomb’s law. This numerical simulation is dedicated to study the electrostatic effect on particle behavior and erosion occurred in the dilute particle-laden bend flow. Forces considered acting on particles includes drag, lift, gravity and electrostatic force. Results obtained for the fluid phase are in good agreement with experimental and numerical data. Predictions show that electrostatic field does affect the particle motion in the pipe bend. At higher air flow rate with higher electrostatics at the inner arc the increasement of impact angle is lower than that at lower flow rate with lower electrostatics. The same conclusion can be found at the outer arc. In addition, electrostatic effect does increase particle-wall impact velocity while such trend decreases with flow rate. Erosion rate increases with increasing air flow rate, which is independent of electrostatics. However, given the same flow rate, the electrostatics reduces the occurrence of erosion at the bend. The erosion rate under electrostatic effect is found to approach that without electrostatics as the flow rate increases. Therefore, the effect of electrostatics on erosion decreases with the air flow rate.

BREAKDOWN VOLTAGE OF MICRON RANGE AIR INCLUSIONS IN CAPACITOR PAPER

Purpose. To substantiate the breakdown mechanism of capacitor paper on the basis of numerical-field models with segmented cross-sections of cylindrical volumes of air and water, and also use the proposed models to determine the breakdown strength of air in micron-sized gaps under normal conditions. Methodology. The model bases on a finite element solution to an electrostatic problem in a volume of capacitor paper consisting of cellulose and pores with air and water. First, the possible scenarios for the growth of breakdown in capacitor paper are analyzed and to the conclusion is made, that complete breakdown developed from a partial breakdown in the air cavity. A brand of capacitor paper is chosen in such a way that when its thickness changed, the breakdown strength of the electric field changed over a wide range. Then, for the paper with the lowest average electric field intensity the possibility of explaining the complete breakdown by the breakdown of air segments on the basis of the Paschen dependence is checked. Further points of the obtained dependence by constructing models of papers of the same brand and a different thickness under the assumption of the similarity of electrostatic fields are determined. As such a criterion, the constancy of the equivalent effective permittivity are taken. Results. The dependence of the breakdown strength of the air in the range of 1.36...5.54 μm under normal conditions is determined. The obtained relationship is between the Peschot and Taev curves. Originality. For the first time, the possibility of indirectly estimation the breakdown strength of an insulating material using an electrostatic field model is indicated. Practical value. The proposed method for the numerical calculation of the breakdown voltage of air inclusions in the presence of water inclusions in the thickness of solid insulation can be applied to other types of solid thin-layer insulation.

Analysis of static electric field characteristics of ships in flowing medium

At present, the model of ship corrosion electrostatic field mainly analyzes the electrostatic field distribution in the static medium under the given boundary conditions, without considering the actual corrosion of the metal on the ship’s surface in the flowing seawater, and the relationship between the electrochemical corrosion of the metal and the flow of the medium is very large, which results in a large error between the simulation results and the actual measurement results. In this paper, the relationship between corrosion electrostatic field and flow rate in flowing medium is theoretically deduced. Firstly, the distribution of liquid flow rate is analyzed, the thickness of boundary layer on the surface of metal plate is calculated, then the mass transfer process in flowing electrolyte is calculated by combining the flow rate distribution of metal surface medium, and the corrosion current density on the metal surface under the control of mass transfer process is calculated. Finally, the corrosion current density on the metal surface under the control of mass transfer process is calculated. The equivalent source model of electric field is established based on the current density, and the distribution of corrosion electrostatic field in the medium is analyzed. The correctness of the conclusion is verified by the finite element simulation and the ship model experiment.

Experimental, analytical and numerical analysis of voltage distribution along the cap-and-pin insulators

This paper deals with the experimental, analytical and numerical analysis of voltage distribution along the cap-and-pin insulators. Five different insulators strings are analyzed, consisting of two, three, four, five and six cap-and-pin U40BL glass disc insulators. Experimental measurements are performed in the high voltage laboratory at the Faculty of Electrical Engineering East Sarajevo. Measurement of the voltage distribution along the disc insulators is performed by using measuring sphere gap. Analytical calculations are performed by using mathematical model which considers parasite self-capacitances of disc insulators, as well as their parasite capacitances to the earth and to the phase conductor. Calculations of the parasite capacitances values are performed and optimum values which lead to the minimum difference between measured and calculated results are suggested. Numerical analyses of the non-linear voltage distribution are performed by using electrostatic field model in software Comsol Multyphisics. 2D axisymmetric models of the cap-and-pin insulators are developed. Despite the measuring configuration is not suitable for numerical analysis, relatively good agreement between the measured results and results calculated by using specialized software are achieved.

Dynamic Imaging of Membrane Hydration

Lipid membranes are essential for life: They provide a dynamic compartmentalized environment, a localized space for proteins (e.g. ion channels) to perform their functions, and a selective environment to decide what enters the cell. Although recognized as an essential building block, water is usually treated as a background for biology; mainly because it cannot be measured on the molecular interfacial level of realistic free floating membrane systems. However, water is a crucial mediator of chemical change and determines the structure of the membrane. Water and ions determine the electrostatic environment of the membrane, whether interfacial reactions take place and provide a path for the insertion and functioning of ion channels/pores. The study of lipid membranes is generally pursued by following either a top-down approach, introducing labels to living cell membranes or a bottom-up approach with well-controlled but simplified membrane monolayer or supported membrane models. In the first approach molecular level hydration information is lost, while in the second approach the connection with real bilayer membranes is limited. Recent work in in our laboratory offers an alternative path that ultimately envisions bringing together both top-down and bottom-up approaches. By using intermediate nano-, micro- and macroscale free-floating membrane systems in combination with novel nonlinear optical spectroscopy and imaging methods, we advance the understanding of realistic membranes on a more fundamental level. In this presentation I will introduce those methods and provide an overview of recent advances in understanding membrane molecular structure, hydration, and electrostatics. We demonstrate the failure of electrostatic mean field models, the emerging roles of variable length scale, curvature, confinement and transient ordered water domains by experiments on lipid droplets, liposomes, macroscopic free floating membranes and living neurons.

Surface Characterization of Colloidal Silica Nanoparticles by Second Harmonic Scattering: Quantifying the Surface Potential and Interfacial Water Order.

The microscopic description of the interface of colloidal particles in solution is essential to understand and predict the stability of these systems, as well as their chemical and electrochemical reactivity. However, this description often relies on the use of simplified electrostatic mean field models for the structure of the interface, which give only theoretical estimates of surface potential values and do not provide properties related to the local microscopic structure, such as the orientation of interfacial water molecules. Here we apply polarimetric angle-resolved second harmonic scattering (AR-SHS) to 300 nm diameter SiO2 colloidal suspensions to experimentally determine both surface potential and interfacial water orientation as a function of pH and NaCl concentration. The surface potential values and interfacial water orientation change significantly over the studied pH and salt concentration range, whereas zeta-potential (ζ) values remain constant. By comparing the surface and ζ-potentials, we find a layer of hydrated condensed ions present in the high pH case, and for NaCl concentrations ≥1 mM. For milder pH ranges (pH < 11), as well as for salt concentrations <1 mM, no charge condensation layer is observed. These findings are used to compute the surface charge densities using the Gouy–Chapman and Gouy–Chapman–Stern models. Furthermore, by using the AR-SHS data, we are able to determine the preferred water orientation in the layer directly in contact with the silica interface. Molecular dynamics simulations confirm the experimental trends and allow deciphering of the contributions of water layers to the total response.

Influence of dielectric constant on dielectric strength by defect discharge and molecular polarization in solid insulation materials

Dielectric constant and dielectric strength are two intrinsic electrical parameters of solid insulating materials. In order to finally understand the relationship between them, the one-sided influence of dielectric constant on dielectric strength is investigated. For theoretical analysis, we propose that the influence is realized indirectly by two mechanisms: defect discharge in the micro level and molecular polarization in the nanoscale. The transition phase is composed of the field enhancement related to permittivity and the breakdown of defect molecular bond. While the local field around the bond is always higher than the cavity interior field, the breakdown field is a competition between the two mechanisms. According to the simulation model of electrostatic field, the electric field around the cavity is significantly enhanced with a larger dielectric constant. In view of the simulation result of partial discharge, the discharge intensity of dielectric and gas breakdown in the cavity is promoted by the increase of material permittivity. To confirm the defect distribution and quantity, several prepared samples are scanned with the ultrasonic microscope and the cavities are measured via image software. Based on the published experiment data from oxide films and polymer bulks, a revised relationship is plotted and fitted for the dielectric strength and the dielectric constant. As molecular polarization is applicable to oxide films with few defects and high permittivities, defect discharge is more effective for polymer bulks with generous cavities and low permittivities. Since molecular polarization leads to breakdown by enhancing the local electric field, cavity discharge is mainly due to the lower breakdown threshold of defect.

Study of influencing characteristics on boundary-layer separation controlled by using DBD plasma actuator with modified model

For more effectively utilizing state of the plasma flow characteristics, to control separation of boundary layer from the subsonic to supersonic, the vortex flow, viscous coupling including shock induced separation, to improve combustion stability and efficiency, thereby minimizing the parasitic resistance and controlling separation bubble issue effectively. Therefore, the main research focus of this paper will be divided into two parts. The first part, the experimental design and measurement will be implemented under atmosphere temperature and pressure conditions, including the actuator for driving the high-voltage AC dielectric plasma between the geometric parameters and the actuating voltage and the relationship between the discharge characteristics of actuator. The second part, we apply the finite volume method to solve the Navier-Stokes equations, and combines the modified physical model of electrostatic field. Through the applied AC voltage and charge density equation for solving Maxwell's equations and the way of obtaining an electric field, investigate the dielectric discharge flow affecting the acceleration effects of normal atmospheric pressure plasma and its impact on the boundary layer flows of thin plate. According to the mentioned above, considering the number of different geometric parameters and different actuator free flow conditions, the impact of physical parameters, for instance, electric potential, electric density and body forces which generated by plasma actuator in computational model, and their further interactions with thin plate boundary layer flow, and then the induced velocity field are discussed in detail.

Investigation of electrostatic fields by modeling methods

The environment is filled with electrostatic fields of various origins. The negative influence of the electrostatic field requires the provision of electrostatic safety standards. So modeling of electrostatic fields is a topical research task. The electrization of objects is complex, depending on the many parameters process. The article considers the existing methods of studying electrostatic fields. The authors have justified the criterion for assessing the safety of an electrostatic field. The article proposes the developed advanced mathematical model describing the electrization of a complex, multi-layered object. Variable values in the proposed mathematical model are the main characteristics of the materials forming the layers of the modeled object, and the parameters of the condition of the environment. The constructed mathematical model of electrization of a complex object has undergone a successful experimental verification in field trials. Analysis of the experimental data confirmed the expected condition of the system, which is a complex object.

Optimization of Electrostatic Atomization Cutting Using 3D FE Simulation of Electrostatic Field

Compared with minimal quantity lubrication (MQL), electrostatic atomization can control the movement of mist droplets by changing the electrostatic field, thus reducing the drift of mist droplets in air. This paper first proposes the concept of electrostatic atomization cutting, and then develops a 3D FE model of electrostatic field for electrostatic atomization cutting using a commercial software Ansoft Maxwell. By simulation, the influence of nozzle angle, structure, and electrode gap and voltage on electric field intensity is investigated. Based on simulation results, the optimal nozzle angle and structure are obtained for electrostatic atomization cutting. The findings contribute to further development of this technique.

A direct route for the investigation of crystalline field effects on the spectral properties of Eu3+ ions in designed nanostructures

The spectral properties of lanthanide ions doped in a solid-state matrix, especially the Stark splitting and emission shifts, are strongly influenced by the local crystalline field. Here, we use a direct approach to quantitatively investigate the crystalline field effect on these spectral properties of Eu3+ ions in our designed β-PbF2:Eu3+ and BaF2:Eu3+ nanostructures. The extremely similar structures in which the central Eu3+ ions have the same site symmetry allow the local crystalline field to be simplified as the same point charge electrostatic field model. In this model, the direction and intensity of the electrostatic field are related to the distortion and expansion degree of the charge cloud of the luminescent center, respectively, and further determine the Stark splitting and emission shift. The theoretical analysis and charge-cloud stimulations were in good agreement with the experimental results. The direction and intensity of the crystalline field were calculated, and showed that the emission spectra shift to red with the increase in intensity. This work provides a comprehensive understanding of the spectral changes induced by a crystalline field, which is of great significance for the design of materials with the desired spectral properties.

Use of sensor characterization data to tune electrostatic model parameters for LSST sensors

We build on previous efforts to model CCD sensors, during illumination and collection of conversions. We use a finite summation of simple, electrostatic field models. The upgraded functionality of our framework provides specific predictions for perturbations in pixel boundary enclosures (e.g., at the backside window) and the bookkeeping capability to stack those perturbations so that they may be utilized as Greens functions—portable calculation results that may be generically applied to a range of precision astronomy related problems that naturally include astrometric photometric and shape transfer issues. We approach the topic of using ancillary pixel data, derived from the Greens function and the registered image, to analyze sky data and constrain object parameters of astronomical targets.

Computational Modeling of Electrostatic Charge and Fields Produced by Hypervelocity Impact

Following prior experimental evidence of electrostatic charge separation, electric and magnetic fields produced by hypervelocity impact, we have developed a model of electrostatic charge separation based on plasma sheath theory and implemented it into the CTH shock physics code. Preliminary assessment of the model shows good qualitative and quantitative agreement between the model and prior experiments at least in the hypervelocity regime for the porous carbonate material tested. Moreover, the model agrees with the scaling analysis of experimental data performed in the prior work, suggesting that electric charge separation and the resulting electric and magnetic fields can be a substantial effect at larger scales, higher impact velocities, or both.

Extraction of Magnetic Parameters for Elements of a Planar EMI Filter

The planar electromagnetic interference (EMI) filter has good application in aviation for its easy magnetic integration, small parasitic parameter, and strong anti-EMI ability. Based on the annular structure, the common-mode (CM) and difference-mode (DM) modules are proposed. The former is formed by “capacitance and inductance” (LC unit), while the latter is formed by an independent DM capacitor and the leakage inductance of the LC units. The extraction of the unit-length electromagnetic parameters is the foundation of analyzing the characteristics of the modules and further the whole EMI filter. The axisymmetric electrostatic field model of LC unit is established to extract the turn-to-turn partial capacitances. Considering the skin effect, proximity effect, and core loss, the model of harmonic magnetic field of LC unit is also established to extract the inductances and resistances. To obtain the leakage inductance that serves as the DM inductance, the model of harmonic magnetic field with a leakage layer between LC units is studied. The DM capacitance can be calculated directly using the approximate expression of a parallel plate. Finally, the impedances of the LC units can be drawn out with the obtained distributed parameters under the appreciate boundary conditions, and they are compared with the measured results. The results verify the accuracy of the extracted parameters and the validity of the proposed extraction method.

Multipath Video Real-Time Streaming by Field-Based Anycast Routing

Wireless mesh networking (WMN) for video surveillance provides a strong potential for rapid deployment in a large community, for which reliability and survivability for real-time streaming are the key performance measure. However, current routing protocols do not provide a robust solution to meet video transmission requirements such as providing load balancing for the high data rate and delay requirements. We propose an application of field-based anycast routing (FAR) protocol, which utilizes rapid routing dynamics inspired by an electrostatic potential field model governed by Poisson's equation. This routing metric takes into account geometric proximity and congestion degree in order to increase delivery ratio and decrease end-to-end delay, which determine the quality of the delivered video. In addition, FAR protects node failure with an on-the-fly rerouting process that guarantees the continuity of video streaming. Simulation results show 100% delivery ratio in congestion situations and it shows tolerance to different delay requirements compared with AODV and FDMR protocols in terms of delivering real-time and non real-time video surveillance which verifies FAR as a strong candidate for video transmission over WMN.