An Estimation Method of Electric Field Forces on a Single Bubble

2010 ◽  
Author(s):  
Yaozu Song ◽  
Feng Chen ◽  
Yao Peng
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Theoretical Calculations ◽  
Estimation Method ◽  
Electrode System ◽  
Single Bubble ◽  
Theoretical Formula ◽  
Bubble Behavior ◽  
Electrode Structure ◽  
Electric Field Direction

It has been well-known that externally imposed static electric fields have a significant effect on bubble dynamic behavior, especially on bubble departure behavior. With increasing electric field strength, bubble detachment volume decreases and bubble shape elongates along the electric field direction. It is electric field forces that change bubble behavior. The electric field forces can be calculated from theoretical formula for a simple electrode structure. However, for the complex electrode system, it is rather a tough thing to theoretically solve electric field forces. In this work a new method to experimentally estimate electric field forces exerted on a single bubble has been presented. Experimental estimation primarily depends upon decreasing in the buoyancy on the bubble. Furthermore, the calculations coming from theoretical formula have also been completed and the results show that experimental estimations agree well with theoretical calculations.

scholarly journals Clarifications on the Behavior of Alternative Gases to SF6 in Divergent Electric Field Distributions under AC Voltage

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1065
Author(s):  
Houssem Eddine Nechmi ◽  
Michail Michelarakis ◽  
Abderrahmane (Manu) Haddad ◽  
Gordon Wilson
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Partial Discharge ◽  
Mean Value ◽  
Electrode System ◽  
Polarity Reversal ◽  
Buffer Gas ◽  
Co2 Gas ◽  
Breakdown Mechanism ◽  
Positive Cycle

Negative and positive partial discharge inception voltages and breakdown measurements are reported in a needle-plane electrode system as a function of pressure under AC voltage for natural gases (N2, CO2, and O2/CO2), pure NovecTM gases (C4F7N and C5F10O) and NovecTM in different natural gas admixtures. For compressed 4% C4F7N–96% CO2 and 6% C5F10O–12% O2–82% CO2 gas mixtures, the positive-streamer mode is identified as the breakdown mechanism. Breakdown and negative partial discharge inception voltages of 6% C5F10O–12% O2–82% CO2 are higher than those of 4% C4F7N–96% CO2. At 8.8 bar abs, the breakdown voltage of 6% C5F10O–12% O2–82% CO2 is equal to that of 12.77% O2–87.23% CO2 (buffer gas). Synergism in negative partial discharge inception voltage/electric field fits with the mean value and the sum of each partial pressure individually component for a 20% C4F7N–80% CO2 and 6% C5F10O–12% O2–82% CO2, respectively. In 9% C4F7N–91% CO2, the comparison of partial discharge inception electric fields is Emax (CO2) = Emax(C4F7N), and Emax (12.77% O2–87.23% CO2) = Emax(C5F10O) in 19% C5F10O–81%(12.77% O2–87.23% CO2). Polarity reversal occurs under AC voltage when the breakdown polarity changes from negative to positive cycle. Polarity reversal electric field EPR was quantified. Fitting results show that EPR (CO2) = EPR(9% C4F7N–91% CO2) and EPR(SF6) = EPR (22% C4F7N–78% CO2). EPR (4% C4F7N–96% CO2) = EPR (12.77% O2–87.23% CO2) and EPR (6% C5F10O–12% O2–82% CO2) < EPR (4% C4F7N–96% CO2) < EPR (CO2).

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.

Flow and Species Transport Control in Grooved Micro-Channels

2005 ◽  
Author(s):  
Jungyoon Hahm ◽  
Ali Beskok
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Mixing Time ◽  
Micro Channel ◽  
Complex Flow ◽  
Species Transport ◽  
Micro Channels ◽  
Electric Field Direction ◽  
Transport Control ◽  
Dependent Flow

We demonstrate flow control concepts in a grooved micro-channel using selectively patterned, electroosmotically active surfaces and locally applied electric fields. This framework enables formation of rather complex flow patterns in simple micro-geometries. Ability to vary the electric field magnitude and its polarity also manifests time-dependent flow alterations, which results in flow and species transport control abilities. The results obtained in a single micro-groove constitute the proof of concept for flow and species transport control in an integrated serial micro-fluidic process, where multiple species can be trapped and released in prescribed amounts in a micro-channel with multiple grooves. The groove size determines volume of the entrapped species. In addition, each groove can simultaneously contain one or two species at the same time. The proposed flow and species transport control scheme allows control over the interspecies diffusion and mixing time and length scales by simply adjusting the electric field direction and its magnitude. We envision utilization of flow and species transport in a grooved micro channel, where combinatorial chemistry experiments can be performed using multiple grooves, where each groove can be addressed (filled, emptied or mixed) independently.

Bubble Formation and Detachment Under the Influence of Electric Fields and the Role of Gravity

2005 ◽  
Author(s):  
C. Herman ◽  
Z. Liu ◽  
E. Iacona
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Heated Surface ◽  
Gravity Level ◽  
Reduced Gravity ◽  
Bubble Behavior ◽  
Transfer Coefficients ◽  
High Heat Transfer ◽  
The Impact ◽  
Bubble Removal

Boiling is an attractive solution to cooling problems in aerospace engineering because of the high heat transfer coefficients associated with phase change processes. Bubble detachment from an orifice shows some resemblance to bubble departure in boiling. The buoyancy force is responsible for bubble removal from the surface in terrestrial conditions. In space, with the gravity level being orders of magnitude smaller than on earth, bubbles formed during boiling can remain attached to the surface. As a result, the amount of heat removed from the heated surface can decrease, and it is difficult to predict reliably and accurately. The impact of electric fields is investigated with the aim to control bubble behavior and help bubble removal from the surface on which they form in reduced gravity. The behavior of single gas bubbles injected through an orifice into an electrically insulating liquid is studied in reduced gravity under the influence of static electric fields and the results of the experiments are compared with data obtained using a simplified model. The bubble life cycle was visualized in terrestrial conditions and reduced gravity. Bubble departure, volume and dimensions at detachment were measured and analyzed for different parameters such as gravity level, electric field magnitude and electric field uniformity. Results suggest that these parameters significantly affect bubble behavior, shape, volume and dimensions at detachment.

Bubble Detachment in Variable Gravity Under the Influence of Electric Fields

2002 ◽  
Author(s):  
Cila Herman ◽  
Shinan Chang ◽  
Estelle Iacona
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
High Speed ◽  
Bubble Formation ◽  
Experimental Studies ◽  
Video Camera ◽  
Contact Angles ◽  
Uniform Electric Field ◽  
Bubble Behavior ◽  
Insulating Liquid

The objective of the research is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static electric field. Situations were considered with both uniform and nonuniform electric fields. Bubble formation and detachment were visualized in terrestrial gravity as well as for several levels of reduced gravity (lunar, martian and microgravity) using a high-speed video camera. Bubble volume, dimensions and contact angles at detachment were measured. In addition to the experimental studies, a simple model, predicting bubble characteristics at detachment in an initially uniform electric field was developed. The model, based on thermodynamic considerations, accounts for the level of gravity as well as the magnitude of the uniform electric field. The results of the study indicate that the level of gravity and the electric field magnitude significantly affect bubble behavior as well as shape, volume and dimensions.

Influence of Electric Fields on the Fracture Behavior of Ferroelectric Ceramics under Combined Electromechanical Loading

2006 ◽  
Vol 306-308 ◽  
pp. 1199-1204 ◽  
Author(s):  
Zhan Wei Liu ◽  
Dai Ning Fang ◽  
Hui Min Xie
Keyword(s):  
Fracture Toughness ◽  
Electric Field ◽  
Electric Fields ◽  
Crack Extension ◽  
Fracture Behavior ◽  
Ferroelectric Ceramics ◽  
Normal Strain ◽  
Electric Field Direction ◽  
Poling Direction ◽  
Electromechanical Loading

In this paper, fracture behavior of ferroelectric ceramics under combined electromechanical loading was investigated using moiré interferometry. It is found that the influence of electric field on fracture toughness is not very larger in the case that the directions of the poling, electric field and crack extension are perpendicular to each other. When the poling direction is parallel to the crack extension direction and both are perpendicular to the electric field direction, the normal strain measured reduced faster than that calculated by FEM with and without electrical loading as the distance away from the crack tip increases. Fracture toughness decreases obviously as the electric-field intensity increases.

scholarly journals Surface Charge Properties of Epoxy Composites under DC Voltage Affected by Surface and Bulk Conductivity

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 370
Author(s):  
Qian Wang ◽  
Xidong Liang ◽  
Ke Chen ◽  
Chao Wu ◽  
Shan Liu
Keyword(s):  
Electric Field ◽  
Surface Charge ◽  
Epoxy Resin ◽  
Electric Fields ◽  
Surface Resistivity ◽  
Resin Composites ◽  
Charge Accumulation ◽  
Electrode Structure ◽  
Epoxy Resin Composites ◽  
High Electric Fields

As DC transmission voltage increases, the DC wall bushing becomes longer, and a supporting insulator is introduced to keep the conductor straight. Under extremely high electric fields coupled with a thermal gradient, the surface charge of the supporting insulator may distort the field distribution and increase the risk of flashover. In this paper, surface potentials of three model epoxy resin composites were systematically investigated under varied voltage amplitudes, different voltage polarities and electric field distributions. The bulk and surface resistivity of the epoxy resin composites over a broad temperature range were measured to reveal the correlations between surface charge and such basic electrical parameters. The results indicate that the normal-dominated electric field plays the major role in charge accumulation. The processes of surface charge accumulation and dissipation are more closely related to the surface resistivity. As a result, the surface charge properties can be improved by optimizing the electrode structure and resistivity of the epoxy resin composites.

scholarly journals Investigation of the Electro-Optical Characteristics of GaAs/AlGaAs Multiple Quantum Well Grown by Metal Organic Vapor Phase Epitaxy

2021 ◽  
Author(s):  
Aslan Turkoglu ◽  
Yüksel Ergun
Keyword(s):  
Electric Field ◽  
Quantum Wells ◽  
Electric Fields ◽  
Vapor Phase ◽  
Theoretical Calculations ◽  
Energy Levels ◽  
Vapor Phase Epitaxy ◽  
Multiple Quantum ◽  
Organic Vapor ◽  
Metal Organic

Abstract In this study, the photoluminescence measurements of GaAs/AlGaAs multi-quantum-wells heterojunction structure grown on n+-GaAs substrates by Metal Organic Vapor Phase Epitaxy (MOVPE) method are investigated. By dropping 5145 Å wavelength laser light on the sample at room temperature and low temperatures, the transitions between the bands in the structure and the changes in these transitions under the different electric fields and temperatures are observed. In addition, by making theoretically developed self-consistent potential calculations, the subband energy levels and their corresponding wave functions of the structure under the electric field and without the electric field are calculated. The obtained numerical results were found to be in full agreement with the experimental measurements and theoretical calculations.

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