Disintegration of pairs of water drops in an electric field

1966 ◽  
Vol 295 (1440) ◽  
pp. 84-97 ◽  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
High Speed ◽  
Local Fields ◽  
Radius Of Curvature ◽  
Theoretical Treatment ◽  
Rigid Spheres ◽  
Cloud Droplets ◽  
Water Drops ◽  
Good Agreement

In his theoretical treatment of the deformation and disintegration of individual water drops of undistorted radius R 0 situated in an electric field, Taylor assumed that the drop retained a spheroidal shape until the instability point was reached and that the equations of equilibrium between the stresses due to surface tension, T , the electric field, F , and the difference between the external and internal pressures was satisfied at the poles and the equator. He calculated that the onset of instability occurs when F ( R 0 / T ) ½ = 1.625, which is in good agreement with experiment. Taylor’s assumptions have been applied to the problem of the disintegration of pairs of water drops of identical undistorted radii R 0 separated in an electric field with their line of centres parallel to the field. As F increases, the drops deform and eventually one of them disintegrates in a lower field than would be necessary for an individual drop owing to the enhancement of the local field between the drop caused by the mutual interactions of the polarization charges. On the basis of values calculated by Davis for the field enhancement between pairs of rigid spheres, values of F ( R 0 / T )½ at the disintegration point were computed. These ranged from Taylor’s value of 1.625 for large separations to 1.555, 9.889 x 10 -1 , 7.887 x 10 -2 , 3.910 x 10 -3 and 1.898 x 10 -4 for initial separations of 10, 1, 0.1, 0.01 and 0.001 radii respectively. These values of F ( R 0 / T ) ½ are slightly reduced for larger drops owing to the influence of the hydrostatic pressure difference between their vertical extremities. These calculations were tested experimentally on suspended drops and good agreement was obtained. Mass and charge were transferred from the disintegrating drop to its neighbour. Measurements taken from high speed photographs of the radius of curvature and the elongation of a drop at the moment of disintegration agreed quite closely with the predicted values. These studies indicate that the inductive mechanism of cloud electrification will separate appreciable quantities of charge even if the prevailing electric fields are weak provided that a small fraction of the interactions between polarized drops are not followed by coalescence. Numerical values for the elongation of cloud droplets as a function of their separation are presented, which should be utilized in accurate computations of cloud droplet trajectories within electrified clouds. The studies also demonstrate that the local fields between impinging cloud droplets are numerically adequate, even if the external fields are weak, to cause disintegration of one of the droplets, which is generally accompanied by the passage of a filament of water to the other drop, thus penetrating the air film separating the two drops and promoting their coalescence.

The vibration of electrified water drops

1971 ◽  
Vol 322 (1551) ◽  
pp. 523-534 ◽  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Axial Ratio ◽  
Uniform Electric Field ◽  
Interferometric Technique ◽  
Photographic Analysis ◽  
Wide Range ◽  
Water Drops ◽  
Strength And Deformation ◽  
A Charge

Pressure has been used as the principal parameter in calculations of the fundamental vibrational frequencies of spherical drops of radius R , density ρ, and surface tension T carrying a charge Q or uncharged spheroidal drops of axial ratio a / b situated in a uniform electric field of strength E . Freely vibrating charged drops have a frequency f = f 0 ( 1 - Q 2 /16π R 3 T ) ½ , as shown previously by Rayleigh (1882) using energy considerations; f 0 is the vibrational frequency of non-electrified drops (Rayleigh 1879). The fundamental frequency of an uncharged drop in an electric field will decrease with increasing field strength and deformation a / b and will equal zero when E ( R )/ T ) ½ = 1.625 and a / b = 1.86; these critical values correspond to the disintegration conditions derived by Taylor (1964). An interferometric technique involving a laser confirmed the accuracy of the calculations concerned with charged drops. The vibration of water drops of radius around 2 mm was studied over a wide range of temperatures as they fell through electric fields either by suspending them in a vertical wind tunnel or allowing them to fall between a pair of vertical electrodes. Photographic analysis of the vibrations revealed good agreement between theory and experiment over the entire range of conditions studied even though the larger drops were not accurately spheroidal and the amplitude of the vibrations was large.

Effect of a High Electric Field on the Thermal and Phase Change Characteristics of an Impacting Drop

2019 ◽  
Author(s):  
Abhishek Basavanna ◽  
Prajakta Khapekar ◽  
Navdeep Singh Dhillon
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Phase Change ◽  
Electric Fields ◽  
High Speed ◽  
Impact Behavior ◽  
Liquid Drops ◽  
Active Interest ◽  
Post Impact ◽  
High Electric Fields

Abstract The effect of applied electric fields on the behavior of liquids and their interaction with solid surfaces has been a topic of active interest for many decades. This has important implications in phase change heat transfer processes such as evaporation, boiling, and condensation. Although the effect of low to moderate voltages has been studied, there is a need to explore the interaction of high electric fields with liquid drops and bubbles, and their effect on heat transfer and phase change. In this study, we employ a high speed optical camera to study the dynamics of a liquid drop impacting a hot substrate under the application of high electric fields. Experimental results indicate a significant change in the pre- and post-impact behavior of the drop. Prior to impact, the applied electric field elongates the drop in the direction of the electric field. Post-impact, the recoil phase of the drop is significantly affected by charging effects. Further, a significant amount of micro-droplet ejection is observed with an increase in the applied voltage.

The Electric Field Measuring by Phase Selective Photoreflectance

1996 ◽  
Vol 421 ◽  
Author(s):  
J. S. Hwang ◽  
W. Y. Chou ◽  
S. L. Tyan ◽  
Y. C. Wang ◽  
H. Shen
Keyword(s):  
Electric Field ◽  
Theoretical Calculation ◽  
Buffer Layer ◽  
Electric Fields ◽  
Phase Angle ◽  
Substrate Interface ◽  
Field Measuring ◽  
Lock In ◽  
Good Agreement ◽  
Reference Phase

AbstractThe built-in electric fields in a MBE grown δ-doped GaAs homojunction have been investigated by the techniques of photoreflectance and phase suppression. Two Franz-Keldysh oscillation features originating from two different fields in the structure superimpose with each other in the photoreflectance spectrum. By properly selecting the reference phase of the lock-in amplifier, one of the features can be suppressed, thus enabling us to determine the electric fields from two different regions. We have demonstrated that only two PR spectra, in-phase and outphase components, are needed to find the phase angle which suppresses one of the features. The electric field in the top layer is 3.5 ± 0.2 × 105 V/cm, which is in good agreement with theoretical calculation. The electric field in the buffer layer is 1.2 ± 0.1 × 104 V/cm, which suggests the existence of interface states at the buffer/substrate interface.

ELECTRIC FIELD INFLUENCE ON TRAVELING WAVE PROPAGATION AND STATIONARY PATTERN FORMATION

1995 ◽  
Vol 05 (03) ◽  
pp. 797-807 ◽  
Author(s):  
J. MOSQUERA ◽  
M. GÓMEZ-GESTEIRA ◽  
V. PÉREZ-MUÑUZURI ◽  
A.P. MUÑUZURI ◽  
V. PÉREZ-VILLAR
Keyword(s):  
Wave Propagation ◽  
Pattern Formation ◽  
Electric Field ◽  
Electric Fields ◽  
Traveling Wave ◽  
Traveling Fronts ◽  
Spatial Terms ◽  
Oregonator Model ◽  
Field Influence ◽  
Good Agreement

The electric field influence on pattern formation and traveling wave propagation is investigated in the framework of the Oregonator model. When an electric field is applied to a system that can suffer spatial instabilities, Turing and Turing-like patterns (traveling fronts that become stationary patterns when reaching a zero-flux boundary) are observed. On the other hand, when an electric field is applied to a system that cannot become unstable by spatial terms and where wavefronts are propagating in the absence of electric fields, the velocity of these wavefronts is modified and can even be reversed. This is in good agreement with previous experimental results.

Elastic Constants of Nematic Liquid Crystals

1972 ◽  
Vol 27 (6) ◽  
pp. 966-976 ◽  
Author(s):  
Hans Gruler ◽  
Terry J. Scheffer ◽  
Gerhard Meier
Keyword(s):  
Magnetic Fields ◽  
Electric Fields ◽  
Detailed Comparison ◽  
Theoretical Treatment ◽  
Electrical Capacitance ◽  
Normal Deformation ◽  
Electric And Magnetic Fields ◽  
The Magnetic Field ◽  
Dynamic Phenomena ◽  
Good Agreement

Abstract We present a theoretical treatment and give experimental observations of the deformation that occurs in a nematic liquid crystal when electric or magnetic fields are applied. We consider only normal deformations in the nematic material where fluid flow and other dynamic phenomena play no role. Three important sample geometries are considered in the magnetic field, and the experimentally observed deformations are in good agreement with theory. The normal deformation induced by electric fields is of interest from a device standpoint, and we give a solution for the deformation that is valid even for large dielectric anisotropics. This solution has been experimentally verified. We give a detailed comparison of the distortions produced by electric and magnetic fields and show that the deformations are of a similar form even though the field is nonuniform in the electric case. The change in birefringence and electrical capacitance as a function of distortion is discussed as a means of observing the deformation.

Electrorheology

MRS Bulletin ◽  
1991 ◽  
Vol 16 (8) ◽  
pp. 38-43 ◽  
Author(s):  
Therese C. Jordan ◽  
Montgomery T. Shaw
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
High Speed ◽  
Flow Properties ◽  
Electric Field Effects ◽  
Properties Of Materials ◽  
Strong Electric Fields ◽  
Silica Suspensions ◽  
Type Of Behavior ◽  
Damping Systems

The influence of electric fields on the deformation and flow properties of materials has been a subject of interest for many years. Recently, there has been renewed interest in a particular branch of these electric field effects—the electrorheological (ER) effect. The ER effect is also known as the Winslow effect after its founder Willis Winslow. Winslow observed that applying strong electric fields to nonaqueous silica suspensions activated with a small amount of water caused rapid solidification of the originally fluid material. This type of behavior was seen as instrumental in the development of high-speed valves, reactive damping systems, and a host of other applications.

scholarly journals Solar and geomagnetic activity effects on mid-latitude F-region electric fields

2008 ◽  
Vol 26 (9) ◽  
pp. 2911-2921 ◽  
Author(s):  
V. V. Kumar ◽  
M. L. Parkinson ◽  
P. L. Dyson ◽  
R. Polglase
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Geomagnetic Activity ◽  
High Speed ◽  
Theoretical Models ◽  
Solar Flux ◽  
Quiet Time ◽  
F Region ◽  
Diurnal Patterns ◽  
Ae Index

Abstract. Diurnal patterns of average F-region ionospheric drift (electric field) and their dependence on solar and geomagnetic activity have been defined using digital ionosonde Doppler measurements recorded at a southern mid-latitude station (Bundoora 145.1° E, 37.7° S geographic, 49° S magnetic). A unique database consisting of 300 907 drift velocities was compiled, mostly using one specific mode of operation throughout 1632 days of a 5-year interval (1999–2003). The velocity magnitudes were generally larger during the night than day, except during the winter months (June–August), when daytime velocities were enhanced. Of all years, the largest drifts tended to occur during the high speed solar wind streams of 2003. Diurnal patterns in the average quiet time (AE<75 nT) meridional drifts (zonal electric field) peaked at up to ~6 m s−1 poleward (0.3 mV m−1 eastward) at 03:30 LST, reversing in direction at ~08:30 LST, and gradually reaching ~10 m s−1 equatorward at ~13:30 LST. The quiet time zonal drifts (meridional electric fields) displayed a clear diurnal pattern with peak eastward flows of ~10 m s−1 (0.52 mV m−1 equatorward) at 09:30 LST and peak westward flows around midnight of ~18 m s−1 (0.95 mV m−1 poleward). As the AE index increased, the westward drifts increased in amplitude and they extended over a greater fraction of the day. The perturbation drifts changed in a similar way with decreasing Dst except the daytime equatorward flows strengthened with increasing AE index, whereas they became weak for Dst<−60 nT. The responses in all velocity components to changing solar flux values were small, but net poleward perturbations during the day were associated with large solar flux values (>192×10−22 W m−2 Hz−1). These results help to more fully quantify the response of the mid-latitude ionosphere to changing solar and geomagnetic conditions, as required to refine empirical and theoretical models of mid-latitude electric fields.

Elastic Behavior of a Rubber Layer Bonded between Two Rigid Spheres

1988 ◽  
Vol 61 (4) ◽  
pp. 630-638 ◽  
Author(s):  
A. N. Gent ◽  
Y-C. Hwang
Keyword(s):  
Elastic Behavior ◽  
Theoretical Treatment ◽  
Rigid Spheres ◽  
Rubber Layer ◽  
Axial Tensile ◽  
Compression Stiffness ◽  
Axis Of Symmetry ◽  
Set Up ◽  
Thick Layers ◽  
Good Agreement

Abstract Finite-element methods (FEM) have been employed to calculate the stresses set up in a thin rubber layer, bonded between two rigid spheres, when small tensile or compressive deflections are imposed. Values of stiffness have been calculated for various spacings of the spheres, i.e., for various thicknesses of the rubber layer. They are in good agreement with earlier experimental measurements of compression stiffness and with the predictions of an approximate theoretical treatment. However, they are strongly affected by small departures of the rubber layer from complete incompressibility. The highest dilatant stress (in tension) is found to be set up on the central axis, near the bonded surfaces, where internal failure has been observed to occur in similar bonded layers. For moderately thick layers, the axial tensile stress in the center of the layer is substantially higher than the lateral stresses. This feature suggests that the initiation of failure in this location may not obey the same criterion as for an isotropic stress field, and that a crack, once formed here, will propagate as a tear across the axis of symmetry.

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.

Surface morphologies of electrospun polystyrene fibers induced by an electric field

2019 ◽  
Vol 89 (18) ◽  
pp. 3850-3859 ◽  
Author(s):  
Na Meng ◽  
Yuansheng Zheng ◽  
Binjie Xin
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Applied Voltage ◽  
High Speed ◽  
Three Dimensional ◽  
Electrospinning Process ◽  
Fiber Morphology ◽  
Jet Behavior ◽  
Working Distance ◽  
Surface Morphologies

The electric field plays a key role in the formation of fibers during the electrospinning process. The electric field strength and shape caused by the applied voltage between the spinneret and collector govern the electrospinning process. In this study, a comprehensively designed and correctly implemented analysis was carried out to investigate the effects of the electric field on jet behavior and fiber morphology. Both working distance and applied voltage, respectively, were adjusted to manipulate the electric field shape and strength. The three-dimensional electric fields were simulated to understand the electric field distribution; in addition, a high-speed camera was adopted to capture the images of jet motion. Four parameters, namely straight jet length, envelope cone, height of the bending area, and velocity of the bending jet, were measured to describe the jet behavior. It can be revealed that the shape and strength of the electric field are responsible for the jet behavior and the fiber morphology, which include resultant ripples, grooves, and pores.

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