A dielectric fluid drop in an electric field

1969 ◽  
Vol 312 (1511) ◽  
pp. 473-494 ◽  
Keyword(s):  
Electric Field ◽  
Applied Field ◽  
Dielectric Permeability ◽  
Uniform Electric Field ◽  
Dielectric Fluid ◽  
Equilibrium Configurations ◽  
Prolate Spheroids ◽  
Fluid Drop ◽  
Equilibrium Shapes ◽  
The Moment

In this paper an appropriate extension of the virial method developed by Chandrasekhar is used to systematically re-examine the equilibrium and stability of an incompressible dielectric fluid drop situated in a uniform electric field. The equilibrium shapes are initially assumed to be ellipsoidal; and it is shown that only prolate spheroids elongated in the direction of the applied field are compatible with the moment equations of lowest order. The relation between the equilibrium elongation a/b and the dimensionless parameter x = FR 1/2 /T 1/2 , where F is the applied field, R = ( ab 2 ) 1/2 , and T is the surface tension, is obtained for every dielectric permeability e . This relation is monotonic if e ≤ 20.801; but if 20.801 < e < ∞, there exist as many as three different equilibrium elongations (configurations) for some values of x less than 2.0966. Conditions for the onset of instability are obtained from an examination of the characteristic frequencies of oscillation associated with secondharmonic deformations of the equilibrium configurations. Dielectrics having e > 20.801 exhibit instability while those having e ≤ 20.801 do not. In the former case, where there are three different equilibrium configurations for the same value of x , only the middle one is unstable.

Deformation of a fluid drop subjected to a uniform electric field

2021 ◽  
Vol 72 (1) ◽  
Author(s):  
Youness Filali ◽  
Mustapha Er-Riani ◽  
Mustapha El Jarroudi
Keyword(s):  
Electric Field ◽  
Uniform Electric Field ◽  
Fluid Drop

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.

Effect of Quincke Rotation and Taylor Circulation on Mass Transfer from a Fluid Drop in a Constant Electric Field

2011 ◽  
Vol 312-315 ◽  
pp. 259-264
Author(s):  
Tov Elperin ◽  
A. Fominykh
Keyword(s):  
Mass Transfer ◽  
Electric Field ◽  
Similarity Transformation ◽  
Constant Electric Field ◽  
Analytical Form ◽  
Uniform Electric Field ◽  
Two Dimensional ◽  
Convective Mass Transfer ◽  
Fluid Drop ◽  
Quincke Rotation

We consider non-stationary convective mass transfer in a binary system comprising a stationary dielectric two-dimensional fluid drop embedded into an immiscible dielectric liquid under the influence of a constant uniform electric field. The partial differential equation of diffusion is solved by means of a similarity transformation, and the solution is obtained in a closed analytical form. Dependence of Sherwood number vs. the strength of the applied electric field is analyzed. It is shown that an electric field can be used for enhancement of the rate of mass transfer in terrestrial and reduced gravity environments.

Effect of Viscosity Ratio on the Electric-Field-Driven Enhancement of Heat/Mass Transfer to a Spherical Drop

2012 ◽  
Author(s):  
Mohamed R. Abdelaal ◽  
Milind A. Jog
Keyword(s):  
Mass Transfer ◽  
Electric Field ◽  
Mass Transport ◽  
Heat Mass Transfer ◽  
Viscosity Ratio ◽  
Continuous Phase ◽  
Uniform Electric Field ◽  
Dielectric Fluid ◽  
Periodic Electric Field ◽  
Time Periodic

The effect of viscosity ratio on the electric-field-driven enhancement of heat/mass transfer to a spherical liquid drop of one dielectric fluid from another immiscible dielectric fluid is computationally investigated in this paper. The flow field is considered to be in the Stokes regime and the energy (species) conservation equations in the continuous phase are solved numerically using a fully implicit finite volume method. Results for flow outside the drop, transient temperature distributions, Nusselt number variations, and heat/mass transfer enhancement are presented for Peclet numbers varying from 10 to 500, dimensionless electric field frequency from 50 to 1000, and the ratio of viscosity of the continuous to the dispersed phase varying from 0.1 to 50. Steady and non-uniform unsteady electric fields are considered. The computational simulations show that when viscosity of the drop is lower than the viscosity of the surrounding fluid, a steady uniform electric field is more effective in enhancement of heat/mass transport compared to a non-uniform time periodic electric field. Conversely, when the continuous phase is less viscous than the drop, the non-uniform time periodic electric field provides improved heat/mass transport than the steady uniform electric field.

scholarly journals Numerical computation of the domain of operation of an electrospray of a very viscous liquid

2010 ◽  
Vol 648 ◽  
pp. 35-52 ◽  
Author(s):  
F. J. HIGUERA
Keyword(s):  
Shear Stress ◽  
Electric Field ◽  
Electric Current ◽  
Viscous Liquid ◽  
Stationary Solution ◽  
Flow Rate ◽  
Electric Charge ◽  
Applied Field ◽  
Dielectric Fluid ◽  
Viscous Shear

A numerical study is carried out of the injection of a very viscous liquid of small electrical conductivity at a constant flow rate through an orifice in a metallic plate under the action of an electric field. The conditions under which the injected liquid can form an elongated meniscus with a thin jet emanating from its tip are investigated by computing the flow, the electric field and the transport of electric charge in the meniscus and a leading region of the jet. A stationary solution is found only for values of the flow rate above a certain minimum. At moderate values of the applied field, this minimum flow rate decreases when the applied field or the conductivity of the liquid increase. The electric shear stress acting on the surface of the liquid is not able to drive the liquid into the jet at flow rates smaller than the minimum while, for any flow rate higher than the minimum, the transfer of electric current to the surface may occur in a slender region of the jet where charge relaxation effects are small and the field induced by the electric charge of the jet is important. At high values of the applied field, the flow rate must be higher than another minimum, which increases with the applied field, in order for the viscous stress to balance the strong electric stress acting on the meniscus. The two conditions taken together determine lower and upper bounds for the applied field at a given flow rate, but the value of the applied field at which a stationary jet is first established when this parameter is gradually increased is higher than the lower bound, leading to hysteresis. When the liquid is electrosprayed in a surrounding dielectric fluid, the viscous shear stress that this fluid exerts on the surface of the jet eventually balances the electric shear stress and stops the continuous stretching of the jet. A fraction of the conduction current is left in the jet when the effect of the outer liquid comes into play in the region where this current is transferred to the surface, and no stationary solution is found above a maximum flow rate that decreases when the viscosity of the outer liquid increases or the applied field decreases. Order of magnitude estimates of the electric current and the conditions in the current transfer region are worked out.

A rotating spherical liquid drop in an electric field

1972 ◽  
Vol 56 (2) ◽  
pp. 305-312 ◽  
Author(s):  
C. Sozou
Keyword(s):  
Electric Field ◽  
Equilibrium Shape ◽  
Dielectric Fluid ◽  
Inviscid Fluid ◽  
Axis Of Rotation ◽  
Field Parallel ◽  
Electric Field Parallel ◽  
Fluid Drop ◽  
The Stability ◽  
Small Deformations

It is shown that the equilibrium shape of an incompressible dielectric fluid drop rotating with constant angular velocity in the presence of a uniform external electric field of appropriate magnitude along the axis of rotation is spherical. For an inviscid fluid drop, the stability of this spherical configuration to small deformations is investigated by means of Chandrasekhar's virial method. We find that a rotating drop in the presence of an electric field parallel to the axis of rotation is, in some respects, more stable than when either only the electric field or only rotation is present. This is due to the fact that the application of an electric field parallel to the axis of a rotating drop, or of rotation parallel to an electric field in which a drop is immersed, shifts the instability mechanism to another normal mode.

Dielectrophoretic Rotation in Budding Yeast Cells

1980 ◽  
Vol 35 (11-12) ◽  
pp. 1111-1113 ◽  
Author(s):  
Maja Mischel ◽  
Ingolf Lamprecht
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Budding Yeast ◽  
Low Frequency ◽  
Rotation Frequency ◽  
Moment Of Inertia ◽  
Yeast Cells ◽  
Uniform Electric Field ◽  
The Moment

Abstract Rotation of budding yeast cells in an alternating non-uniform electric field of low frequency was investigated. Rotation frequency was found to be proportional to field strength above a threshold, and varied from cell to cell. The threshold is inversely correlated with the moment of inertia of the cells, while the slope of rotation frequency versus field strength increases with the moment. Rotation frequencies varied between 1 and 10 cycles per second. Clear differences between the dielectrophoretic behaviour of living and heat-inactivated yeast cells were observed.

scholarly journals The Changing Shape of a Liquid Drop in an Electric Field

2013 ◽  
Vol 3 ◽  
pp. 24-40
Author(s):  
A.A.S.N. Jayalal ◽  
K.A.I.L. Wijewardena Gamalath
Keyword(s):  
Surface Tension ◽  
Dielectric Constant ◽  
Aspect Ratio ◽  
Electric Field ◽  
Applied Electric Field ◽  
Applied Field ◽  
Cone Angle ◽  
Constant Ratio ◽  
Spherical Drop ◽  
Fluid Drop

An approximate extension of the slender body theory was used to determine the static shape of a conically ended dielectric fluid drop in an electric field. Using induced surface charge density, hydrostatic pressure and the surface tension of the liquid with interfacial tension stresses and Maxwell electric stresses, a governing equation was obtained for slender geometries for the equilibrium configuration and numerically solved for 3D. For an applied electric field, the electric energy on a spherical drop can be maximized in a weak dielectric by increasing the applied electric field. The minimum dielectric constant ratio needed to produce a conical end is 14.5 corresponding to a cone angle 31.25° .There is a sharp increment of the aspect ratio after reaching the threshold value of the applied field strength and the deformation of the fluid drop increases with the increase in dielectric constant of the fluid drop. For a particular dielectric constant ratio, the threshold electric field producing conical interface increases with the increased surface tension of the liquid. The threshold electric field for a water drop is 1.0854×104 units and the corresponding aspect ratio is 15. For the minimum dielectric ratio the cone angle of the drop decreases with applied field making the drop more stable at higher fields.

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