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C. G. Garton

Bio: C. G. Garton is an academic researcher. The author has contributed to research in topics: Electrostriction & Dielectric. The author has an hindex of 1, co-authored 1 publications receiving 201 citations.

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TL;DR: In this article, it was shown that a bubble of gas or liquid, immersed in a liquid medium and subjected to an electric field between parallel plate electrodes, assumes the shape of a prolate spheroid in the direction of the field.
Abstract: It is shown that a bubble of gas or liquid, immersed in a liquid medium and subjected to an electric field between parallel plate electrodes, assumes the shape of a prolate spheroid in the direction of the field. Expressions for interfacial traction between two fluid dielectrics, if derived by taking into account electrostriction (Stratton 1941; Smythe 1950), are shown to be in disagreement with experimental results and must therefore be considered incorrect. Using expressions for interfacial traction not involving electrostrictive terms, equations are derived for the dependence on electric stress of the elongation of compressible (gaseous) and of incompressible (liquid) bubbles immersed in an insulating liquid. These show that as the field strength is increased, conducting bubbles, and also non-conducting bubbles for which the permittivity of the bubble exceeds twenty times the permittivity of the medium, elongate until a critical shape is reached when the bubble becomes unstable. For conducting bubbles the critical shape corresponds to a ratio of the major to the minor semi-axis of 1*85. Bubbles of permittivity ratio lower than 20 have no critical shape, the axial ratio increasing indefinitely with increase of field strength. There is satisfactory agreement between theory and experiment. The implications of these results with regard to electrical breakdown of liquids are discussed.

206 citations


Cited by
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01 Jul 2002-Polymer
TL;DR: In this paper, an electrospinning method was used to fabricate bioabsorbable amorphous poly( d, l -lactic acid) (PDLA) and semi-crystalline poly( l-lactic acids) (PLLA) nanofiber non-woven membranes for biomedical applications.

1,779 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive account of streamer propagation in dielectric fluids in point-plane geometries is presented, and the relation between shock wave and streamer velocities is investigated.
Abstract: In this paper we present a comprehensive account of our results on streamer propagation in dielectric fluids in point‐plane geometries. Propagation velocities for both positive and negative streamers have been determined as a function of the following parameters: temperature, pressure, density, viscosity, composition, and conductivity. Effects of voltage and interelectrode spacing were examined. Current and light emission during streamer growth were measured. The relation between shock wave and streamer velocities was investigated. Small concentrations of low‐ionization potential additives markedly accelerated the positive streamers, while electron scavengers accelerated the negative streamers. Mechanisms to account for these observations are discussed.

372 citations

Journal ArticleDOI
TL;DR: In this article, the authors considered a drop of fluid, initially held spherical by surface tension, will deform when an electric or magnetic field is applied, and the deformation will depend on the electric/magnetic properties (permittivity/permeability and conductivity) of the drop and the surrounding fluid.
Abstract: A drop of fluid, initially held spherical by surface tension, will deform when an electric or magnetic field is applied. The deformation will depend on the electric/ magnetic properties (permittivity/permeability and conductivity) of the drop and of the surrounding fluid. The full time-dependent low-Reynolds-number problem for the drop deformation is studied by means of a numerical boundary-integral technique. Fluids with arbitrary electrical properties are considered, but the viscosities of the drop and of the surrounding fluid are assumed to be equal. Two modes of breakup have been observed experimentally : (i) tip-streaming from drops with pointed ends, and (ii) division of the drop into two blobs connected by a thin thread. Pointed ends are predicted by the numerical scheme when the permittivity of the drop is high compared with that of the surrounding fluid. Division into blobs is predicted when the conductivity of the drop is higher than that of the surrounding fluid. Some experiments have been reported in which the drop deformation exhibits hysteresis. This behaviour has not in general been reproduced in the numerical simulations, suggesting that the viscosity ratio of the two fluids can play an important role.

347 citations

Journal ArticleDOI
TL;DR: In this paper, the Galerkin finite-element method with an elliptic mesh generation scheme was used to solve the nonlinear free-boundary problem composed of the Navier-Stokes system governing flow field and Laplace's system governing electric field.
Abstract: Axisymmetric steady flows driven by an electric field about a deformable fluid drop suspended in an immiscible fluid are studied within the framework of the leaky dielectric model. Deformations of the drop and the flow fields are determined by solving the nonlinear free-boundary problem composed of the Navier-Stokes system governing the flow field and Laplace's system governing the electric field. The solutions are obtained by using the Galerkin finite-element method with an elliptic mesh generation scheme. Under conditions of creeping flow and vanishingly small drop deformations, the results of finite-element computations recover the asymptotic results. When drop deformations become noticeable, the asymptotic results are often found to underestimate both the flow intensity and drop deformation. By tracking solution branches in parameter space with an arc-length continuation method, curves in parameter space of the drop deformation parameter D versus the square of the dimensionless field strength E usually exhibit a turning point when E reaches a critical value Ec. Along such a family of drop shapes, steady solutions do not exist for E > Ec. The nonlinear relationship revealed computationally between D and E2 appears to be capable of providing insight into discrepancies reported in the literature between experiments and predictions based on the asymptotic theory. In some special cases with fluid conductivities closely matched, however, drop deformations are found to grow with E2 indefinitely and no critical value Ec is encountered by the corresponding solution branches. For most cases with realistic values of physical properties, the overall electrohydrodynamic behaviour is relatively insensitive to effects of finite-Reynolds-number flow. However, under extreme conditions when fluids of very low viscosities are involved, computational results illustrate a remarkable shape turnaround phenomenon: a drop with oblate deformation at low field strength can evolve into a prolate-like drop shape as the field strength is increased.

187 citations

Journal ArticleDOI
TL;DR: In this article, the authors describe results from a new series of experiments where drops suspended in weakly conducting liquids were deformed into spheroids with both steady and oscillatory fields.
Abstract: When an electric field is applied to a drop suspended in another liquid the drop deforms. The relation between the applied field and the mode and magnitude of the deformation have been studied extensively. Nevertheless, Torza, Cox & Mason (1971) found that quantitative agreement between the leaky dielectric theory (Taylor 1966) and experiment is quite poor. Here we describe results from a new series of experiments. Drops suspended in weakly conducting liquids were deformed into spheroids with both steady and oscillatory fields. Drop deformation, interfacial tension, and the electrical properties of the fluids were measured for each system to provide a definitive test of the theory. The agreement between the leaky dielectric model and our results for drop deformations in steady fields is much improved over previous results, although discrepancies remain for some systems. Drop deformations in oscillatory fields consist of steady and oscillatory parts because of the quadratic dependence on the field strength. Measurements of the steady part at 60 Hz, where the oscillatory deformation is negligible, are in excellent agreement with the theory. The effects of frequency on the steady deformation were studied by measuring oblate deformations at a series of frequencies and field strengths; the agreement with theory is good. Finally, the time-dependent total deformation was measured under conditions where both parts of the deformation are commensurate. Good agreement was found between the measured and predicted maximum and minimum deformations. Nevertheless, only a small range of fluid properties could be studied owing to the need to avoid droplet sedimentation.

183 citations