Effect of an electric field on the stability of binary dielectric fluid mixtures

2020 ◽  
Vol 152 (23) ◽  
pp. 234901
Author(s):  
Jonathan M. Martin ◽  
Kris T. Delaney ◽  
Glenn H. Fredrickson
Keyword(s):  
Electric Field ◽  
Dielectric Fluid ◽  
Fluid Mixtures ◽  
The Stability

Effect of Horizontal Alternating Current Electric Field on the Stability of Natural Convection in a Dielectric Fluid Saturated Vertical Porous Layer

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
B. M. Shankar ◽  
Jai Kumar ◽  
I. S. Shivakumara
Keyword(s):  
Natural Convection ◽  
Electric Field ◽  
Prandtl Number ◽  
Traveling Wave ◽  
Effective Viscosity ◽  
Darcy Number ◽  
Wave Mode ◽  
Dielectric Fluid ◽  
Fluid Viscosity ◽  
The Stability

The stability of natural convection in a dielectric fluid-saturated vertical porous layer in the presence of a uniform horizontal AC electric field is investigated. The flow in the porous medium is governed by Brinkman–Wooding-extended-Darcy equation with fluid viscosity different from effective viscosity. The resulting generalized eigenvalue problem is solved numerically using the Chebyshev collocation method. The critical Grashof number Gc, the critical wave number ac, and the critical wave speed cc are computed for a wide range of Prandtl number Pr, Darcy number Da, the ratio of effective viscosity to the fluid viscosity Λ, and AC electric Rayleigh number Rea. Interestingly, the value of Prandtl number at which the transition from stationary to traveling-wave mode takes place is found to be independent of Rea. The interconnectedness of the Darcy number and the Prandtl number on the nature of modes of instability is clearly delineated and found that increasing in Da and Rea is to destabilize the system. The ratio of viscosities Λ shows stabilizing effect on the system at the stationary mode, but to the contrary, it exhibits a dual behavior once the instability is via traveling-wave mode. Besides, the value of Pr at which transition occurs from stationary to traveling-wave mode instability increases with decreasing Λ. The behavior of secondary flows is discussed in detail for values of physical parameters at which transition from stationary to traveling-wave mode takes place.

scholarly journals Effect of Horizontal AC Electric Field on the Stability of Natural Convection in a Vertical Dielectric Fluid Layer

2016 ◽  
Vol 9 (6) ◽  
pp. 3073-3086 ◽  
Author(s):  
B. M. Shankar ◽  
J. Kumar ◽  
I. S. Shivakumara ◽  
S. B. Naveen Kumar ◽  
◽  
...  
Keyword(s):  
Natural Convection ◽  
Electric Field ◽  
Fluid Layer ◽  
Dielectric Fluid ◽  
Ac Electric Field ◽  
The Stability

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.

Electrohydrostatic instability in electrically stressed dielectric fluids. Part 2

1975 ◽  
Vol 72 (1) ◽  
pp. 95-112 ◽  
Author(s):  
D. H. Michael ◽  
J. Norbury ◽  
M. E. O'Neill
Keyword(s):  
Electric Field ◽  
Point Of View ◽  
Dielectric Fluid ◽  
Sufficient Information ◽  
Physical Point ◽  
Dielectric Fluids ◽  
A Value ◽  
Asymmetric Equilibria ◽  
The Stability ◽  
Loading Parameter

The paper is the second part of a study of the failure of the insulation of a layer of dielectric fluid of arbitrary volume, occupying a hole in a solid dielectric sheet, when stressed by an applied electric field. In part 1 symmetric and asymmetric equilibria were found for the two-dimensional problem, using an approximation given by Taylor (1968) for the electric field, which is valid for large holes. In this paper axisymmetric equilibria are given for a circular hole, under the same conditions. In addition the points of bifurcation of asymmetric solutions have been found, and provide sufficient information to give the stability characteristics. It is found that when the volume-excess fraction δ exceeds a value of approximately −0·3 instability occurs in an asymmetric form reported earlier for large holes by Michael, O'Neill & Zuercher (1971) in the case δ = 0. For δ < −0·3 the nature of the instability changes to an axisymmetric form of failure associated with a maximum of the loading parameter.The analysis given shows that axisymmetric displacements of ‘sausage’ mode type, that is, symmetric about a centre-plane, are associated with small changes in the static pressure in the dielectric layer. Such modes have not previously been examined in this context, and in an appendix to this paper Michael & O'Neill give an analysis of them when δ = 0, valid for all hole sizes, by extending the small perturbation analysis of Michael, O'Neill & Zuercher. These modes however do not provide the most unstable displacements for any configuration, and do not therefore affect the stability from a physical point of view.

Directionality and the Role of Polarization in Electric Field Effects on Radical Stability

2017 ◽  
Vol 70 (4) ◽  
pp. 367 ◽  
Author(s):  
Ganna Gryn'ova ◽  
Michelle L. Coote
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Radical Reactions ◽  
Electric Field Effects ◽  
Dissociation Energies ◽  
Barrier Heights ◽  
Diol Dehydratase ◽  
Group A ◽  
Activity Of Enzymes ◽  
The Stability

Accurate quantum-chemical calculations are used to analyze the effects of charges on the kinetics and thermodynamics of radical reactions, with specific attention given to the origin and directionality of the effects. Conventionally, large effects of the charges are expected to occur in systems with pronounced charge-separated resonance contributors. The nature (stabilization or destabilization) and magnitude of these effects thus depend on the orientation of the interacting multipoles. However, we show that a significant component of the stabilizing effects of the external electric field is largely independent of the orientation of external electric field (e.g. a charged functional group, a point charge, or an electrode) and occurs even in the absence of any pre-existing charge separation. This effect arises from polarization of the electron density of the molecule induced by the electric field. This polarization effect is greater for highly delocalized species such as resonance-stabilized radicals and transition states of radical reactions. We show that this effect on the stability of such species is preserved in chemical reaction energies, leading to lower bond-dissociation energies and barrier heights. Finally, our simplified modelling of the diol dehydratase-catalyzed 1,2-hydroxyl shift indicates that such stabilizing polarization is likely to contribute to the catalytic activity of enzymes.

scholarly journals Electro-responsive polyelectrolyte-coated surfaces

2017 ◽  
Vol 199 ◽  
pp. 335-347 ◽  
Author(s):  
V. Sénéchal ◽  
H. Saadaoui ◽  
J. Rodriguez-Hernandez ◽  
C. Drummond
Keyword(s):  
Electric Field ◽  
Smart Materials ◽  
Electrical Stimulus ◽  
Colloidal Dispersions ◽  
Polymer Chains ◽  
Molecular Response ◽  
Coated Surfaces ◽  
The Stability ◽  
Induced Changes ◽  
Applied Fields

The anchoring of polymer chains at solid surfaces is an efficient way to modify interfacial properties like the stability and rheology of colloidal dispersions, lubrication and biocompatibility. Polyelectrolytes are good candidates for the building of smart materials, as the polyion chain conformation can often be tuned by manipulation of different physico-chemical variables. However, achieving efficient and reversible control of this process represents an important technological challenge. In this regard, the application of an external electrical stimulus on polyelectrolytes seems to be a convenient control strategy, for several reasons. First, it is relatively easy to apply an electric field to the material with adequate spatiotemporal control. In addition, in contrast to chemically induced changes, the molecular response to a changing electric field occurs relatively quickly. If the system is properly designed, this response can then be used to control the magnitude of surface properties. In this work we discuss the effect of an external electric field on the adhesion and lubrication properties of several polyelectrolyte-coated surfaces. The influence of the applied field is investigated at different pH and salt conditions, as the polyelectrolyte conformation is sensitive to these variables. We show that it is possible to fine tune friction and adhesion using relatively low applied fields.

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