Journal of Electrostatics最新文献

The electric potential and field of a finite conducting rod are calculated. This is done by two methods. In the first, ellipsoidal coordinates are used to solve the Laplace equation outside the rod. In the second, asymptotic behavior of the electric field is used to find the position-dependence of the change density on the rod, which is then used to calculate the potential and field. An analytic continuation is performed to relate this problem to that of a conducting disk. Using this, the electric potential and field of a disk are determined. The charge densities are also calculated.

In a quiescent environment, dielectric barrier discharge (DBD) plasma actuators generate a wall jet through the interaction of ionized and neutral molecules in an electric field. In external flow, the coupling between electrohydrodynamic (EHD), turbulence, inertial, and viscous effects in the flow boundary layer is more complex and requires additional investigation. We experimentally study momentum injection by DBD actuators into the free stream flow with Re = 35,000 and 75,000 in co-flow and counter-flow scenarios over a range of V_AC = 12 kV–19.5 kV peak-to-peak at a frequency of 2 kHz. In co-flow, the momentum injection leads to boundary layer thinning and fluid entrainment from the freestream into the DBD forcing region, while in the counter-flow configuration, flow separation can occur. A separation bubble is observed at Re = 35,000 for the tested condition. The momentum difference in the counter-flow configuration is six times greater than the EHD jet momentum in a quiescent environment. Both co-flow and counter-flow momentum injections show diminishing effects with higher Re. We show that the resulting flow pattern is not a superposition of the EHD jet and the free stream but is determined by the coupling and competition of inertial, viscous, and Coulombic effects between the EHD-driven forcing and the external flow. The proposed non-dimensional momentum ratio (M*) of EHD jet momentum to momentum in the external flow boundary layer can be used to predict the onset of separation; however, additional experimental and numerical studies are required to generalize this concept to other flow scenarios. The velocity profiles and momentum measurements presented here can be used to validate numerical models and inform the design of DBD actuators for active flow control.

Accurate determination of the electrostatic force exerted on multipole moments is essential in comprehending the interaction between charged bodies and dielectric layers. A comprehensive solution is presented in this study for the calculation of the electric potential, field, and force generated by nth-order electric multipole above a semi-infinite dielectric body covered by a dielectric layer using the image multipole method. The present study investigates the impact of dielectric thickness, permittivity, and separation distance on the electrostatic interaction between an electric multipole moment and a semi-infinite dielectric body. The calculation results indicate that as the thickness of the dielectric layer increases and the dielectric constant of the surrounding medium surpasses that of the dielectric layer, the electrostatic attractive force undergoes a transition to a repulsive force. The magnitude of the electrostatic force acting on a nth-order electric multipole moment is directly proportional to the square of the value of the electric multipole moment and inversely proportional to the 2 (n+1) power of the distance.

Numerical values of electrostatic properties of the cube are well investigated whereas numerical ones of the square plate are not. In this paper, we update the numerical values of electrostatic properties of the unit square plate, such as the capacitance, and the edge and corner singularity exponents. For the capacitance, we use the refined Brownian dynamics algorithm with “walk-on-planes” (WOP) method (a kind of first-passage algorithm) and for the edge singularity and corner exponents, the sphere last-passage algorithm.

This study investigates particle dynamics impacting a charged spherical collector through experiments and simulations, revealing the influence of the collector’s non-uniform potential field. Electrostatic and drag forces govern trajectories, while gravity and dielectrophoretic forces play a minor role. Positive electrostatic and negative drag work are comparable, offering critical insights into particle energy budgets. Closer proximity to the collector center leads to a greater energy budget, causing uneven particle collection. Analysis of fractional energy loss indicates a critical point where electrostatic work dominates over viscous dissipation. This analysis is crucial for analyzing particle deposition behavior in non-uniform electric fields.

—When the particles are in the gas-solid two-phase flow, the transferred charge will be generated. The transferred signal obtained by using the inner flush-mounted electrostatic sensor is rich in flow information, which can provide important support for studying the flow law of gas-solid two-phase flow. In this paper, the nonlinear time-domain analysis method based on embedded empirical mode decomposition (EEMD) and largest Lyapunov exponent (LLE) is proposed to extract the transferred charge signal of gas-solid two-phase flow. Firstly, the electrostatic signal is decomposed and the induced charge signal is removed by the combination of EEMD and autocorrelation function correlation coefficient index. Then, the LLE of the remaining intrinsic mode function (IMF) components is calculated, and the corresponding IMF is selected to reconstruct into the transferred charge signal according to the condition that LLE>0. The results show that the LLE of transferred charge signal increases with the increase of the superficial gas velocity and decreases with the increase of solid gas mass ratio. The root mean square (RMS) and standard deviation (STD) of the transferred charge signal increase with the increase of the superficial gas velocity, increase with the increase of the solid gas mass ratio, and slow down at high solid gas mass ratio.

This paper presents numerical and experimental investigations of electrohydrodynamic (EHD) flow and solid extraction during melting of phase-change materials (PCMs) in a rectangular cavity under constant temperature boundary conditions. It was found that EHD generated electroconvection cells in the liquid PCM between each pair of electrodes. The fluid velocity increased with applied voltage and decreased under higher temperature gradients across the liquid region due to buoyancy suppression. In the experimental study, the high-speed imaging at the solid-liquid interface showed that dendrites were extracted from the mushy zone during EHD melting and moved upwards into the liquid bulk under the action of the interfacial EHD forces.

Electrospray deposition (ESD) was utilized for targeted nutrient and water delivery to the roots of lettuce plants. Compatibility of ESD with nutrient solutions was confirmed; however, detrimental effects of ESD electric fields/current on plant growth were observed. To overcome this, a novel approach called “Staticaponics" was introduced by separating current and mass transport of ESD using a grounded metal mesh surrounding the root zone. This combination of ESD along with aeroponic and hydroponic concepts was shown to have higher nutrient solution use efficiency than either hydroponic or aeroponic growth alone, with acceptable plant nutrient content in the resulting plant tissue.

The present study examines the use of a two-stage electrohydrodynamic (EHD) gas pump with its electrodes assembly anchored at one corner of a square channel to modify the characteristics of flow inside the channel. Specifically, the proposed EHD pump is examined for its effectiveness in enhancing flow mixing as well as reducing the power requirement. The present study is also aimed at confirming one of the important conclusions drawn from the authors’ earlier works that, given the same number of emitting electrodes, the performance of an EHD pump can be specifically tailored by rearranging the location and orientation of the electrodes so that the modified characteristics of flow can achieve the desired effect. To evaluate the effectiveness of the proposed electrode configuration, the performance of the pump is compared with that of a previous study in which a two-stage gas pump utilizes an electrode assembly mounted on the two parallel walls. For both pumps, the emitting electrodes are flush mounted on the channel walls so that the air flow produced is similar to that of a wall jet. Through the performance assessment, the results obtained from the present study can provide useful information for practical applications of EHD gas pumps.

the mathematical models of glow discharge in transverse (y-direction) and axial (z-direction) magnetic fields are established in this paper. Firstly, Paschen's law is modified for different cross fields. The results show that the breakdown voltage first decreases and then increases with the increase of y-direction magnetic field at the same pressure. The breakdown voltage of glow discharge in z-direction magnetic field increases with the increase of magnetic field. Secondly, the effects of y-magnetic field and z-magnetic field on glow discharge are compared and analyzed by using the modified ionization coefficient. The results show that the plasma density has an extreme value under the combined action of y-direction magnetic field and air pressure. At the same pressure, the plasma density first increases and then decreases with the increase of magnetic field. The larger the magnetic field, the more obvious the plasma attenuation. In the z-direction magnetic field, the plasma density increases with the increase of air pressure or magnetic field.