Electrohydrodynamic Kelvin-Helmholtz Instability of Two Rotating Dielectric Fluids

1998 ◽  
Vol 53 (1-2) ◽  
pp. 17-26
Author(s):  
Mohamed Fahmy El-Sayed
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Rotation Frequency ◽  
Short Wave ◽  
Surface Charges ◽  
Rotation Surface ◽  
Dielectric Fluids ◽  
Fluid Velocities ◽  
Conditions Of Stability

Abstract A linear stability analysis of a novel electrohydrodynamic Kelvin-Helmholtz system consisting of the superposition of two uniformly rotating dielectric media is presented. The characteristic equation for such an arrangement is derived, which in turn yields a stability criterion for velocity differences of disturbances at a given rotation frequency. The conditions of stability for long and short wave perturbations are obtained, and their dependence on rotation, surface tension and applied electric field is discussed. Limiting cases for vanishing fluid velocities, rotation frequency, and applied electric field are also discussed. Under suitable limits, results of previous works are recovered. A detailed analysis for tangential and normal applied electric fields, in the presence and absence of surface charges, is carried out.

Activation of CO2 on Copper Surfaces: The Synergy Between Electric Field, Surface Morphology and Excess Electrons

2020 ◽  
Author(s):  
Amin Jafarzadeh ◽  
Kristof M. Bal ◽  
Annemie Bogaerts ◽  
Erik C. Neyts
Keyword(s):  
Surface Morphology ◽  
Electric Field ◽  
Surface Charge ◽  
External Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Marginal Effect ◽  
Electric Field Effect ◽  
Surface Charges ◽  
Copper Surfaces

<p>In this work we use DFT calculations to study the combined effect of external electric fields, surface morphology and surface charge on CO<sub>2</sub> activation over Cu (111), Cu (211), Cu (110) and Cu (001) surfaces. We observe that the binding energy of the CO<sub>2</sub> molecule on Cu surfaces rises significantly upon increasing the applied electric field strength. In addition, rougher surfaces respond more effectively to the presence of the external electric field towards facilitating the formation of a carbonate-like CO<sub>2</sub> structure and the transformation of the most stable adsorption mode from physisorption to chemisorption. The presence of surface charges further strengthens the electric field effect and consequently gives rise to an improved bending of the CO<sub>2</sub> molecule and C-O bond length elongation. On the other hand, a net charge in the absence of externally applied electric field shows only a marginal effect on CO<sub>2</sub> binding. The chemisorbed CO<sub>2</sub> is more stable and further activated when the effects of an external electric field, rough surface and surface charge are combined. These results can help to elucidate the underlying factors that control CO<sub>2</sub> activation in heterogeneous and plasma catalysis, as well as in electrochemical processes.</p>

Effect of Electric Field on a 3D Rising Bubble in Viscous Fluids

2013 ◽  
Author(s):  
Qingzhen Yang ◽  
Yang Liu ◽  
Ben Q. Li ◽  
Yucheng Ding
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Phase Field Model ◽  
Coupled Model ◽  
Viscous Force ◽  
Field Equations ◽  
Navier Stokes Equation ◽  
Dielectric Fluids ◽  
Rising Bubble

Understanding of a rising bubble in fluid with the presence of external fields is of fundamental importance in boiling heat transfer and gas-liquid flows. In this paper, a computational methodology is presented for a modeling study of hydrodynamic behavior of a bubble rising in fluid subject to an applied electric field. The computational model is developed by solving the Navier-Stokes equation coupled with the phase field model and electric field equations. The coupled model is capable of predicting the evolution of electric field, bubble motion and deformation and the medium fluid. Numerical simulations were conducted to study the combined effect of coupled electrical force, gravity, surface tension and viscous force on the deformation and motion of a bubble as it ascends through the liquid. The liquid and gas are considered as the dielectric fluids and both vertical and horizontal electric fields are studied. The in-house Fortran code was developed to enable the simulation, and numerical results are presented showing that the deformation and rising speed of the bubble are affected by the applied electric field in both magnitude and direction.

Activation of CO2 on Copper Surfaces: The Synergy Between Electric Field, Surface Morphology and Excess Electrons

2020 ◽  
Author(s):  
Amin Jafarzadeh ◽  
Kristof M. Bal ◽  
Annemie Bogaerts ◽  
Erik C. Neyts
Keyword(s):  
Surface Morphology ◽  
Electric Field ◽  
Surface Charge ◽  
External Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Marginal Effect ◽  
Electric Field Effect ◽  
Surface Charges ◽  
Copper Surfaces

<p>In this work we use DFT calculations to study the combined effect of external electric fields, surface morphology and surface charge on CO<sub>2</sub> activation over Cu (111), Cu (211), Cu (110) and Cu (001) surfaces. We observe that the binding energy of the CO<sub>2</sub> molecule on Cu surfaces rises significantly upon increasing the applied electric field strength. In addition, rougher surfaces respond more effectively to the presence of the external electric field towards facilitating the formation of a carbonate-like CO<sub>2</sub> structure and the transformation of the most stable adsorption mode from physisorption to chemisorption. The presence of surface charges further strengthens the electric field effect and consequently gives rise to an improved bending of the CO<sub>2</sub> molecule and C-O bond length elongation. On the other hand, a net charge in the absence of externally applied electric field shows only a marginal effect on CO<sub>2</sub> binding. The chemisorbed CO<sub>2</sub> is more stable and further activated when the effects of an external electric field, rough surface and surface charge are combined. These results can help to elucidate the underlying factors that control CO<sub>2</sub> activation in heterogeneous and plasma catalysis, as well as in electrochemical processes.</p>

Electric-Field Induced Formation of Superconducting Granular Balls

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2529-2535
Author(s):  
R. Tao ◽  
X. Xu ◽  
Y. C. Lan
Keyword(s):  
Surface Energy ◽  
Electric Field ◽  
Liquid Nitrogen ◽  
Applied Electric Field ◽  
Strong Electric Field ◽  
Particle Surface ◽  
Cooper Pairs ◽  
Surface Charges

When a strong electric field is applied to a suspension of micron-sized high T c superconducting particles in liquid nitrogen, the particles quickly aggregate together to form millimeter-size balls. The balls are sturdy, surviving constant heavy collisions with the electrodes, while they hold over 106 particles each. The phenomenon is a result of interaction between Cooper pairs and the strong electric field. The strong electric field induces surface charges on the particle surface. When the applied electric field is strong enough, Cooper pairs near the surface are depleted, leading to a positive surface energy. The minimization of this surface energy leads to the aggregation of particles to form balls.

INFLUENCE OF THE MAGNETIC FIELD ON THE TRANSVERSE RUNAWAY THRESHOLD

2007 ◽  
Vol 21 (10) ◽  
pp. 1715-1720 ◽  
Author(s):  
NANA METREVELI ◽  
ZAUR KACHLISHVILI ◽  
BEKA BOCHORISHVILI
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Nonlinear Oscillations ◽  
Hot Electrons ◽  
Total Field ◽  
Practical Applications ◽  
Energy And Momentum ◽  
The Magnetic Field

The transverse runaway (TR) is a phenomenon whereby for a certain combination of energy and momentum scattering mechanisms of hot electrons, and for a certain threshold of the applied electric field, the internal (total) field tends to infinity. In this work, the effect of the magnetic field on the transverse runaway threshold is considered. It is shown that with increasing magnetic field, the applied critical electric fields relevant to TR decrease. The obtained results are important for practical applications of the TR effect as well as for the investigation of possible nonlinear oscillations that may occur near the TR threshold.

Effect of Electric Field Strength on Texture Evolution of IF Steel Sheet during Annealing

2012 ◽  
Vol 706-709 ◽  
pp. 2617-2621
Author(s):  
Chang Shu He ◽  
Xiang Zhao ◽  
Wei Ping Tong ◽  
Liang Zuo
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Steel Sheet ◽  
Texture Evolution ◽  
If Steel ◽  
X Ray Diffraction ◽  
If Steel Sheet

Specimens cut from a cold-rolled IF steel sheet of 1 mm thickness were respectively annealed at 750°C for 20min under a range of DC electric fields (1kV/cm~4kV/cm). The Effect of electric field strength on recrystallization texture of IF steel sheet was studied by mean of X-ray diffraction ODF analysis. It was found that γ-fiber textures were notably enhanced as electric field strength increased. The strength of γ-fiber textures got their peak values as the applied electric field reached to 4kV/cm. The possible reason for such phenomena was discussed in the viewpoint of interaction between the applied electric field and the orientation-dependent stored-energy in deformed metals which is known as the driving force for recrystallization during annealing.

Electrowetting-Based Coalescence of Droplets During Dropwise Condensation of Humid Air

2019 ◽  
Author(s):  
Enakshi Wikramanayake ◽  
Vaibhav Bahadur
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Growth Dynamics ◽  
Condensation Heat Transfer ◽  
Droplet Growth ◽  
Dropwise Condensation ◽  
Condensation Rate ◽  
Humid Air

Abstract Dropwise condensation yields higher heat transfer coefficients by avoiding the thermal resistance of the condensate film, seen during filmwise condensation. This work explores further enhancement of dropwise condensation heat transfer through the use of electrowetting to achieve faster droplet growth via coalescence of the condensed droplets. Electrowetting is a well understood microfluidic technique to actuate and control droplets. This work shows that AC electric fields can significantly enhance droplet growth dynamics. This enhancement is a result of coalescence triggered by various types of droplet motion (translation of droplets, oscillations of three phase line), which in turn depends on the frequency of the applied AC waveform. The applied electric field modifies droplet condensation patterns as well as the roll-off dynamics on the surface. Experiments are conducted to study early-stage droplet growth dynamics, as well as steady state condensation rates under the influence of electric fields. It is noted that this study deals with condensation of humid air, and not pure steam. Results show that increasing the voltage magnitude and frequency increases droplet growth rate and overall condensation rate. Overall, this study reports more than a 30 % enhancement in condensation rate resulting from the applied electric field, which highlights the potential of this concept for condensation heat transfer enhancement.

scholarly journals Effect of input voltage frequency on the distribution of electrical stresses on the cell surface based on single-cell dielectrophoresis analysis

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Kia Dastani ◽  
Mahdi Moghimi Zand ◽  
Hanie Kavand ◽  
Reza Javidi ◽  
Amin Hadi ◽  
...  
Keyword(s):  
Cell Membrane ◽  
Cell Surface ◽  
Electric Field ◽  
Single Cell ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Structural Changes ◽  
Cell Deformation ◽  
Cell Permeabilization ◽  
Immersed Interface Method

AbstractElectroporation is defined as cell membrane permeabilization under the application of electric fields. The mechanism of hydrophilic pore formation is not yet well understood. When cells are exposed to electric fields, electrical stresses act on their surfaces. These electrical stresses play a crucial role in cell membrane structural changes, which lead to cell permeabilization. These electrical stresses depend on the dielectric properties of the cell, buffer solution, and the applied electric field characteristics. In the current study, the effect of electric field frequency on the electrical stresses distribution on the cell surface and cell deformation is numerically and experimentally investigated. As previous studies were mostly focused on the effect of electric fields on a group of cells, the present study focused on the behavior of a single cell exposed to an electric field. To accomplish this, the effect of cells on electrostatic potential distribution and electric field must be considered. To do this, Fast immersed interface method (IIM) was used to discretize the governing quasi-electrostatic equations. Numerical results confirmed the accuracy of fast IIM in satisfying the internal electrical boundary conditions on the cell surface. Finally, experimental results showed the effect of applied electric field on cell deformation at different frequencies.

Effect of Electromechanical Loadings on Fracture Strength of Piezoelectric Ceramics

2007 ◽  
Vol 353-358 ◽  
pp. 1544-1547
Author(s):  
Byeung Gun Nam ◽  
H.S. Na ◽  
R. Liu ◽  
Katsuhiko Watanabe
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Fracture Strength ◽  
Applied Electric Field ◽  
Crack Extension ◽  
Piezoelectric Ceramics ◽  
Fracture Load ◽  
Open Circuit ◽  
Condition Effect ◽  
Electromechanical Loading

The effect of electromechanical loadings including their sequence, which was motivated by the property of crack energy density for piezoelectric material, was experimentally investigated. Three-point bending fracture test was performed for two piezoelectric ceramics under different electromechanical loading conditions. It was found that the fracture loads under closed circuit condition are greater than those under open circuit condition. Effect of applied electric field on fracture load in the test varied with materials. Applied electric field always enhanced crack extension in C-21 ceramics regardless of their directions, while it produced very little effect on crack extension under negative electric fields in C-2 ceramics. It was also found that electromechanical loading sequence clearly affects fracture strength, although its effect varies also with materials.

scholarly journals Deformation of Emulsion Droplet with Clean and Particle-Covered Interface under an Electric Field

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2984
Author(s):  
Muhammad Salman Abbasi ◽  
Haroon Farooq ◽  
Hassan Ali ◽  
Ali Hussain Kazim ◽  
Rabia Nazir ◽  
...  
Keyword(s):  
Electric Field ◽  
Simulation Model ◽  
Electric Fields ◽  
Applied Electric Field ◽  
Small Deformation ◽  
Spherical Shape ◽  
Emulsion Droplet ◽  
Navier Stokes Equation ◽  
New Findings ◽  
Electric Field Direction

The electrohydrodynamic deformation of an emulsion droplet with a clean and particle-covered interface was explored. Here, the electrohydrodynamic deformation was numerically and experimentally demonstrated under the stimuli of moderate and strong electric fields. The numerical method involves the coupling of the Navier–Stokes equation with the level set equation of interface tracking and the governing equations of so-called leaky dielectric theory. The simulation model developed for a clean interface droplet was then extended to a capsule model for densely particle-covered droplets. The experiments were conducted using various combinations of immiscible oils and particle suspensions while the electric field strength ~105 V/m was generated using a high voltage supply. The experimental images obtained by the camera were post-processed using an in-house image processing code developed on the plat-form of MATLAB software. The results show that particle-free droplets can undergo prolate (deformation in the applied electric field direction) or oblate deformation (deformation that is perpendicular to the direction of the applied electric field) of the droplet interface, whereas the low-conductivity particles can be manipulated at the emulsion interface to form a ‘belt’, ‘helmet’ or ‘cup’ morphologies. A densely particle-covered droplet may not restore to its initial spherical shape due to ‘particle jamming’ at the interface, resulting in the formation of unique droplet shapes. Densely particle-covered droplets behave like droplets covered with a thin particle sheet, a capsule. The deformation of such droplets is explored using a simulation model under a range of electric capillary numbers (i.e., the ratio of the electric stresses to the capillary stresses acting at the droplet interface). The results obtained are then compared with the theory and experimental findings. It was shown that the proposed simulation model can serve as a tool to predict the deformation/distortion of both the particle-free and the densely particle-covered droplets within the small deformation limit. We believe that this study could provide new findings for the fabrication of complex-shaped species and colloidosomes.

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