scholarly journals Lightning Rod Improvement Studies

2000 ◽  
Vol 39 (5) ◽  
pp. 593-609 ◽  
Author(s):  
C. B. Moore ◽  
William Rison ◽  
James Mathis ◽  
Graydon Aulich
Keyword(s):  
Electric Fields ◽  
Local Fields ◽  
Lightning Strike ◽  
Radius Of Curvature ◽  
Lightning Strikes ◽  
Positive Ions ◽  
Wide Range ◽  
Normal Polarity ◽  
Strong Electric Fields ◽  
Tip Radius

Abstract Although lightning rods have long been used to limit damage from lightning, there are currently no American standards for the shape and form of these devices. Following tradition, however, sharp-tipped Franklin rods are widely installed despite evidence that, on occasion, lightning strikes objects in their vicinity. In recent tests of various tip configurations to determine which were preferentially struck by lightning, several hemispherically tipped, blunt rods were struck but none of the nearby, sharper rods were “hit” by lightning. Measurements of the currents from the tips of lightning rods exposed to strong electric fields under negatively charged cloud bases show that the emissions consist of periodic ion charge bursts that act to reduce the strength of the local fields. After a burst of charge, no further emissions occur until that charge has moved away from the tip. Laboratory measurements of the emissions from a wide range of electrodes exposed to strong, normal-polarity thunderstorm electric fields show that positive ions are formed and move more readily over sharp-tipped electrodes than over blunter ones. From these findings, it appears that the electric field rates of intensification over sharp rods must be much greater than those over similarly exposed blunt rods for the initiation of upward-going leaders. Calculations of the relative strengths of the electric fields above similarly exposed sharp and blunt rods show that although the fields, prior to any emissions, are much stronger at the tip of a sharp rod, they decrease more rapidly with distance. As a result, at a few centimeters above the tip of a 20-mm-diameter blunt rod, the strength of the field is greater than that over an otherwise similar, sharper rod at the same height. Since the field strength at the tip of a sharpened rod tends to be limited by the easy formation of ions in the surrounding air, the field strengths over blunt rods can be much stronger than those at distances greater than 1 cm over sharper ones. The results of this study suggest that moderately blunt metal rods (with tip height–to–tip radius of curvature ratios of about 680:1) are better lightning strike receptors than are sharper rods or very blunt ones.

scholarly journals A III B VI PHOTOVOLTAIC RECEPTORS FOR EXPERIMENTAL DETERMINATION OF CARBON COMPOUNDS IN ATMOSPHERE

2016 ◽  
Vol 19 (3) ◽  
Author(s):  
IULIANA CARAMAN ◽  
IGOR EVTODIEV ◽  
OXANA RACOVEŢ ◽  
MARIUS STAMATE
Keyword(s):  
Electric Fields ◽  
Full Range ◽  
Absorption Bands ◽  
Gaseous State ◽  
Wide Range ◽  
Carbon Compounds ◽  
Strong Electric Fields ◽  
Qualitative Measurements ◽  
Semiconductor Type

<p><span lang="EN-US">This paper examines the prospects of using semiconductor layered A<span class="apple-converted-space"> </span><sup>III</sup><span class="apple-converted-space"> </span>B<span class="apple-converted-space"> </span><sup>VI</sup><span class="apple-converted-space"> type -</span> photovoltaic cells<span class="apple-converted-space"> </span>and the photoresis<span class="apple-converted-space">tors</span> as receptors<span class="apple-converted-space"> </span>for quantitative and qualitative measurements of carbon oxides. Carbon compounds in gaseous state form absorption bands of<span class="apple-converted-space"> </span>electromagnetic<span class="apple-converted-space"> </span>radiation in a wide range of spectrum (200 ÷ 100 000) cm<sup>-1</sup>.<span class="apple-converted-space"> </span>The light absorbed<span class="apple-converted-space"> </span>or emitted<span class="apple-converted-space"> </span>in these bands <span class="apple-converted-space">at the</span> excitations with ionizing radiation (X, γ) or strong electric fields contain direct information about the<span class="apple-converted-space"> </span>concentration of these molecules.  The frequencies that<span class="apple-converted-space"> </span>correspond to maxima of these bands are characteristic parameters of absorbing molecules. Fundamental absorption bands of CO, CO<span class="apple-converted-space"> </span><sub>2</sub> and NC have the edge of band at the border of ultraviolet-vacuum, while the emission bands <em>d</em> cover their full range of wave numbers from 45000 cm<sup>-1 </sup>to 10000 cm<sup>-1</sup>. Two types of radiation receptors from lamellar semiconductor type A<sup>III</sup>B<sup>VI</sup><span class="apple-converted-space"> </span>photosensitive in this spectral range are studied.</span></p>

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.

Calculation of the probability of optical transitions in strong electric fields

2000 ◽  
Vol 91 (5) ◽  
pp. 945-951 ◽  
Author(s):  
S. V. Bulyarskii ◽  
N. S. Grushko ◽  
A. V. Zhukov
Keyword(s):  
Electric Fields ◽  
Optical Transitions ◽  
Strong Electric Fields

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.

Electrohydrodynamic rotation of drops at large electric Reynolds numbers

2016 ◽  
Vol 788 ◽  
Author(s):  
Ehud Yariv ◽  
Itzchak Frankel
Keyword(s):  
Electric Fields ◽  
Numerical Solutions ◽  
Fluid Velocity ◽  
Reynolds Numbers ◽  
Mirror Image ◽  
Liquid Drops ◽  
Weakly Conducting ◽  
Strong Electric Fields ◽  
Quincke Rotation ◽  
Asymmetric Solution

When subject to sufficiently strong electric fields, particles and drops suspended in a weakly conducting liquid exhibit spontaneous rotary motion. This so-called Quincke rotation is a fascinating example of nonlinear symmetry-breaking phenomena. To illuminate the rotation of liquid drops we here analyse the asymptotic limit of large electric Reynolds numbers, $\mathit{Re}\gg 1$, within the framework of a two-dimensional Taylor–Melcher electrohydrodynamic model. A non-trivial dominant balance in this singular limit results in both the fluid velocity and surface-charge density scaling as $\mathit{Re}^{-1/2}$. The flow is governed by a self-contained nonlinear boundary-value problem that does not admit a continuous fore–aft symmetric solution, thus necessitating drop rotation. Furthermore, thermodynamic arguments reveal that a fore–aft asymmetric solution exists only when charge relaxation within the suspending liquid is faster than that in the drop. The flow problem possesses both mirror-image (with respect to the direction of the external field) and flow-reversal symmetries; it is transformed into a universal one, independent of the ratios of electric conductivities and dielectric permittivities in the respective drop phase and suspending liquid phase. The rescaled angular velocity is found to depend weakly upon the viscosity ratio. The corresponding numerical solutions of the exact equations indeed collapse at large $\mathit{Re}$ upon the asymptotically calculated universal solution.

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