Numerical Study of Dielectric Fluid Bubble Behavior Within Diverging External Electric Fields

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Matthew R. Pearson ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Mathematical Model ◽  
Electric Field ◽  
Electric Fields ◽  
Numerical Study ◽  
Electrode Spacing ◽  
Small Scale ◽  
Arbitrary Distribution ◽  
Dielectric Fluid ◽  
Reciprocal Effect ◽  
Bubble Deformation

A three-dimensional mathematical model is presented that models bubble deformation of a dielectric fluid due to the presence of a nonuniform electric field and calculates the net dielectrophoretic force that is exerted by the electric field on the bubble. The study includes the development of a method of predicting the shape of a bubble based on the arbitrary distribution of stresses over its surface without requiring an axisymmetric configuration. The reciprocal effect of the bubble’s presence on the electric field is also incorporated into the model, and dimensional analysis is used to obtain a single key parameter that governs the bubble deformation phenomenon. Numerical implementation of the mathematical model shows that the bubble deformation can be significant. Furthermore, bubble deformation and electric field distortion can have significant effects on the dielectrophoretic behavior of bubbles in nonuniform fields, especially within small-scale devices where the bubble size and electrode spacing are similar in magnitude.

Numerical Study of Dynamic Behavior of Dielectric Fluid Bubbles Within Diverging, External Electric Fields

2006 ◽  
Author(s):  
Matthew R. Pearson ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Numerical Study ◽  
Pool Boiling ◽  
Spherical Shape ◽  
Past Research ◽  
Bubble Surface ◽  
Uniform Electric Field ◽  
Dielectric Fluid ◽  
Uniform Field

Past research in the area of pool boiling within the presence of electric fields has generally focused on the case of uniform field intensity. Any numerical or analytical studies of the effect of non-uniform fields on the motion of bubbles within a dielectric liquid medium have assumed that the bubbles will retain their spherical shape rather than deform. These studies also ignore changes to the electrical field caused by the presence of the bubbles. However, these assumptions are not necessarily accurate as, even in the case of a nominally uniform electric field distribution, bubbles can exhibit considerable physical deformation and the field can become noticeably affected in the vicinity of the bubble. This study explores the effect that a non-uniform electric field can have on vapor bubbles of a dielectric fluid by modeling the physical deformation of the bubble and the alteration of the surrounding field. Numerical results show that the imbalance of electrical stresses at the bubble surface exerts a net dielectrophoretic force on the bubble, propelling the bubble to the vicinity of weakest electric field, thereby enhancing the separation of liquid and vapor phases during pool boiling. However, the proximity of the bubble to one of the electrodes can considerably alter the bubble trajectory due to an attractive force that arises from local distortions of the potential and electric fields. This phenomenon cannot be predicted if bubble deformation and field distortion effects are neglected.

scholarly journals Electrostatic forces alter particle size distributions in atmospheric dust

2020 ◽  
Vol 20 (5) ◽  
pp. 3181-3190 ◽  
Author(s):  
Joseph R. Toth III ◽  
Siddharth Rajupet ◽  
Henry Squire ◽  
Blaire Volbers ◽  
Jùn Zhou ◽  
...  
Keyword(s):  
Electric Field ◽  
Size Distribution ◽  
Long Range ◽  
Electric Fields ◽  
Electrostatic Force ◽  
Small Scale ◽  
Size Distributions ◽  
Electrostatic Forces ◽  
Atmospheric Dust ◽  
Airborne Dust

Abstract. Large amounts of dust are lofted into the atmosphere from arid regions of the world before being transported up to thousands of kilometers. This atmospheric dust interacts with solar radiation and causes changes in the climate, with larger-sized particles having a heating effect, and smaller-sized particles having a cooling effect. Previous studies on the long-range transport of dust have found larger particles than expected, without a model to explain their transport. Here, we investigate the effect of electric fields on lofted airborne dust by blowing sand through a vertically oriented electric field, and characterizing the size distribution as a function of height. We also model this system, considering the gravitational, drag, and electrostatic forces on particles, to understand the effects of the electric field. Our results indicate that electric fields keep particles suspended at higher elevations and enrich the concentration of larger particles at higher elevations. We extend our model from the small-scale system to long-range atmospheric dust transport to develop insights into the effects of electric fields on size distributions of lofted dust in the atmosphere. We show that the presence of electric fields and the resulting electrostatic force on charged particles can help explain the transport of unexpectedly large particles and cause the size distribution to become more uniform as a function of elevation. Thus, our experimental and modeling results indicate that electrostatic forces may in some cases be relevant regarding the effect of atmospheric dust on the climate.

Control of Dielectric Fluid Flow Distribution in Micro-Tubes With EHD Conduction Pumping: Numerical Study

2011 ◽  
Author(s):  
Miad Yazdani ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Fluid Flow ◽  
Electric Field ◽  
Conduction Mechanism ◽  
Numerical Study ◽  
Fluid Motion ◽  
Flow Distribution ◽  
Operating Conditions ◽  
Dielectric Fluid ◽  
Total Flow ◽  
Flow Through

The control of fluid flow distribution in micro-scale tubes is numerically investigated. The flow distribution control is achieved via electric conduction mechanism. In electrohydrodynamic (EHD) conduction pumping, when an electric field is applied to a fluid, dissociation and recombination of electrolytic species produces heterocharge layers in the vicinity of electrodes. Attraction between electrodes and heterocharge layers induces a fluid motion and a net flow is generated if the electrodes are asymmetric. The numerical domain comprises a 2-D manifold attached to two bifurcated tubes with one of the tubes equipped with a bank of uniquely designed EHD-conduction electrodes. In the absence of electric field, the total flow supplied at the manifold’s inlet is equally distributed among the tubes. The EHD-conduction, however, operates as a mechanism to manipulate the flow distribution to allow the flow through one branch surpasses the counterpart of the other branch. Its performance is evaluated under various operating conditions.

scholarly journals Electrostatic forces alter particle size distributions in atmospheric dust

2019 ◽  
Author(s):  
Joseph R. Toth III ◽  
Siddharth Rajupet ◽  
Henry Squire ◽  
Blaire Volbers ◽  
Jùn Zhou ◽  
...  
Keyword(s):  
Electric Field ◽  
Size Distribution ◽  
Long Range ◽  
Electric Fields ◽  
Electrostatic Force ◽  
Small Scale ◽  
Size Distributions ◽  
Electrostatic Forces ◽  
Atmospheric Dust ◽  
Airborne Dust

Abstract. Large amounts of dust are lofted into the atmosphere from arid regions of the world before being transported up to thousands of kilometers. This atmospheric dust interacts with solar radiation causing changes in the climate, with larger-sized particles having a heating effect, and smaller-sized particles having a cooling effect. Previous studies on the long-range transport of dust have found larger particles than expected, without a model to explain their transport. Here, we investigate the effect of electric fields on lofted airborne dust by blowing sand through a vertically-oriented electric field, and characterizing the size distribution as a function of height. We also model this system, considering the gravitational, drag, and electrostatic forces on particles, to understand the effects of the electric field. Our results indicate that electric fields keep particles suspended at higher elevations and enrich the concentration of larger particles at higher elevations. We extend our model from the small-scale system to long-range atmospheric dust transport to develop insights on the effects of electric fields on size distributions of lofted dust in the atmosphere. We show that the presence of electric fields and the resulting electrostatic force on particles can help explain the transport of unexpectedly larger particles and cause the size distribution to become more uniform as a function of elevation. Thus, our experimental and modelling results indicate that electrostatic forces should be considered when determining the effect of atmospheric dust on the climate.

The effect of disturbed-time electric fields on the inner plasmasphere

1994 ◽  
Vol 12 (4) ◽  
pp. 296-303 ◽  
Author(s):  
H. F. Balmforth ◽  
R. J. Moffett ◽  
A. J. Smith ◽  
G. J. Bailey
Keyword(s):  
Mathematical Model ◽  
Electric Field ◽  
Electron Density ◽  
Electric Fields ◽  
Doppler Shift ◽  
Group Delay ◽  
Whistler Mode ◽  
L Value

Abstract. Results from a mathematical model provide a description of the mid-latitude, low L-shell ionosphere and plasmasphere. Variations in the composition and dynamics of the plasmasphere and changes in the nature of the coupling between the plasmasphere and the ionosphere are studied for moderately disturbed conditions. Modelled results are compared to group delay and Doppler shift measurements of whistler mode signals at Faraday, Antarctica (L ≈ 2.5), to investigate the effects of disturbed time electric fields on the inner plasmasphere and ionosphere. The disturbed time electric field causes a rapid outward drifting of the plasma leading to a decrease in modelled plasmaspheric electron density at a fixed L-value, which agrees with experimental observations. During the periods of outward drift, the modelled coupling flux is upwards to the plasmasphere which can lead to a significant depletion of NmF2 values.

scholarly journals Radiation Problems Accompanying Carrier Production by an Electric Field in the Graphene

Universe ◽  
2020 ◽  
Vol 6 (11) ◽  
pp. 205
Author(s):  
Sergei P. Gavrilov ◽  
Dmitry M. Gitman ◽  
Vadim V. Dmitriev ◽  
Anatolii D. Panferov ◽  
Stanislav A. Smolyansky
Keyword(s):  
Electromagnetic Field ◽  
Electric Field ◽  
Electric Fields ◽  
Strong Field ◽  
Numerical Study ◽  
Spectral Composition ◽  
General System ◽  
External Electromagnetic Field ◽  
Quantum Radiation ◽  
Quantized Electromagnetic Field

A number of physical processes that occur in a flat one-dimensional graphene structure under the action of strong time-dependent electric fields are considered. It is assumed that the Dirac model can be applied to the graphene as a subsystem of the general system under consideration, which includes an interaction with quantized electromagnetic field. The Dirac model itself in the external electromagnetic field (in particular, the behavior of charged carriers) is treated nonperturbatively with respect to this field within the framework of strong-field QED with unstable vacuum. This treatment is combined with a kinetic description of the radiation of photons from the electron-hole plasma created from the vacuum under the action of the electric field. An interaction with quantized electromagnetic field is described perturbatively. A significant development of the kinetic equation formalism is presented. A number of specific results are derived in the course of analytical and numerical study of the equations. We believe that some of predicted effects and properties of considered processes may be verified experimentally. Among these effects, it should be noted a characteristic spectral composition anisotropy of the quantum radiation and a possible presence of even harmonics of the external field in the latter radiation.

scholarly journals Improving eco-sustainable characteristics and energy efficiency of evaporative fluid cooler via experimental and numerical study

2008 ◽  
Vol 12 (4) ◽  
pp. 89-103 ◽  
Author(s):  
Predrag Raskovic ◽  
Goran Vuckovic ◽  
Mica Vukic
Keyword(s):  
Mathematical Model ◽  
Experimental Study ◽  
Numerical Study ◽  
Simulation Software ◽  
Process Industry ◽  
Small Scale ◽  
Experimental Measurements ◽  
New Approach ◽  
Transfer Processes ◽  
Mass Transfer Processes

This paper presents an on-going research project that aims to identify possibilities for wider use of evaporative cooling in process industry, especially the use of evaporative fluid cooler units. Experimental study is performed on small scale evaporative fluid cooler, while the correlation based model has been carried out to explore the detailed heat and mass transfer processes inside this unit. Numerical integration of mathematical model is executed by new approach, based on differential, collocation Simpson method. Proposed models have been verified by comparing the computed results with those obtained by the experimental measurements. The results of research will enable the creation of more comprehensive simulation software, with wider range of operating and construction parameters.

On the occurrence and characteristics of intense low-altitude electric fields observed by Freja

1995 ◽  
Vol 13 (7) ◽  
pp. 704-712 ◽  
Author(s):  
G. Marklund ◽  
L. Blomberg ◽  
C.-G. Fälthammar ◽  
P.-A. Lindqvist ◽  
L. Eliasson
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Early Morning ◽  
Auroral Oval ◽  
Small Scale ◽  
Auroral Region ◽  
Ion Heating ◽  
Intense Fields ◽  
Auroral Emissions ◽  
Auroral Arcs

Abstract. High-resolution measurements by the double probe electric field instrument on the Freja satellite are presented. The observations show that extremely intense (up to 1 V m–1) and fine-structured (<1 km) electric fields exist at auroral latitudes within the altitude regime explored by Freja (up to 1700 km). The intense field events typically occur within the early morning sector of the auroral oval (01–07 MLT) during times of geomagnetic activity. In contrast to the observations within the auroral acceleration region characterized by intense converging electric fields associated with electron precipitation, upward ion beams and upward field-aligned currents, the intense electric fields observed by Freja are often found to be diverging and located within regions of downward field-aligned currents outside the electron aurora. Moreover, the intense fields are observed in conjunction with precipitating and transversely energized ions of energies 0.5–1 keV and may play an important role in the ion heating. The observations suggest that the intense electric field events are associated with small-scale low-conductivity ionospheric regions void of auroral emissions such as east-west aligned dark filaments or vortex streets of black auroral curls located between or adjacent to auroral arcs within the morningside diffuse auroral region. We suggest that these intense fields also exist at ionospheric altitudes although no such observations have yet been made. This is possible since the height-integrated conductivity associated with the dark filaments may be as low as 0.1 S or less. In addition, Freja electric field data collected outside the auroral region are discussed with particular emphasis on subauroral electric fields which are observed within the 19–01 MLT sector between the equatorward edge of the auroral oval and the inner edge of the ring current.

scholarly journals Critical heat flux enhancement in microgravity conditions coupling microstructured surfaces and electrostatic field

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Alekos Ioannis Garivalis ◽  
Giacomo Manfredini ◽  
Giacomo Saccone ◽  
Paolo Di Marco ◽  
Artyom Kossolapov ◽  
...  
Keyword(s):  
Heat Flux ◽  
Electric Field ◽  
Critical Heat Flux ◽  
Electric Fields ◽  
Parabolic Flight ◽  
Dielectric Fluid ◽  
Two Phase ◽  
Microstructured Surfaces ◽  
Microgravity Conditions ◽  
Plain Surface

AbstractWe run pool boiling experiments with a dielectric fluid (FC-72) on Earth and on board an ESA parabolic flight aircraft able to cancel the effects of gravity, testing both highly wetting microstructured surfaces and plain surfaces and applying an external electric field that creates gravity-mimicking body forces. Our results reveal that microstructured surfaces, known to enhance the critical heat flux on Earth, are also useful in microgravity. An enhancement of the microgravity critical heat flux on a plain surface can also be obtained using the electric field. However, the best boiling performance is achieved when these techniques are used together. The effects created by microstructured surfaces and electric fields are synergistic. They enhance the critical heat flux in microgravity conditions up to 257 kW/m2, which is even higher than the value measured on Earth on a plain surface (i.e., 168 kW/m2). These results demonstrate the potential of this synergistic approach toward very compact and efficient two-phase heat transfer systems for microgravity applications.

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