Electrical Discharge In Water Research Articles

Birthplace of ball lightning

Examples of ball lightning formation at high altitude near a linear lightning channel are considered. A photograph of ball lightning emerging from a linear lightning channel is shown. It is shown that the process of ball lightning formation lasts no more than 30 ms. A model of ball lightning formation due to the action of a magnetic field pulse of a linear lightning current on the ionized volume of space is described. A scheme has been proposed to explain a rare event - the gathering of ball lightning from sparks. Cases of the formation of ball lightning at a large distance from the site of a linear lightning strike, when energy was transferred through wires, are considered. It is noted that the process of formation of such ball lightning and their properties differ markedly from ball lightning appearing near the channel of linear lightning. This made it possible to distinguish these objects into a special type of ball lightning. A model of the process of formation of such ball lightning is described, according to which their core consists of ions flowing from the electrode of an air electrical capacitor (antenna, power line), and the shell material is dust particles. Cases of observation of objects with a size of 50 microns - 1 mm appearing during electrical discharges in water are considered. The analogy of these objects with miniature ball lightning is shown.

Rapid swimmer using explosive boiling due to electrical discharge in water

A strong micro heat engine that can be used in the untethered state is essential for next-generation microrobotics. Here, we propose a rapid swimmer using explosive boiling due to electrical discharge in water. Specifically, we demonstrate that the water-repellent swimmer that has an aluminum discharge antenna in the rear part can swim with the maximum velocity of ∼14 cm/s on the water surface like a water strider between a pair of parallel electrodes in a shallow water pool by applying direct current high-voltage pulses repeatedly. Moreover, by the video observation with high speed (960 fps), we found that an asymmetrical wave was generated immediately after the discharge, and it propelled the swimmer. Our findings should contribute to next-generation microrobots in the future.

Launching phenomenon of a centimeter-scale solid object using explosive boiling due to electrical discharge in water

Technology to launch objects into the air is essential for various applications. In this study, we propose a solid object launcher that pushes the object of centimeter-scale by the rapid liquid motion resulting from explosive vaporization due to electric discharge in water. In particular, by using the electric discharge in a trapezoid-shaped chamber, we demonstrate that a centimeter-scale L-shaped piece of paper with 0.92 mg mass can be launched with an initial velocity ∼4 m/s in the direction of an elevation angle of ∼50°, while a centimeter-scale paper airplane with 29.6 mg mass can be launched with the maximum velocity ∼2 m/s along a glass slide runway with an elevation angle of ∼45°. In addition, to clarify the mechanism of solid launching phenomena, we systematically carried out vertical launching experiments of the centimeter-scale solid object of 60–340 mg. Moreover, as a central design concept peculiar to the solid launching device, we demonstrate the importance of water-repellent treatment of the solid surface. In the future, our device might be used to provide object-shooting technology for hybrid manufacturing technology or to protect orchards from birds.

The danger of ball lightning

Ball lightning in close contact with living beings can strike them with electric current or high-frequency radio emission. The current, passing through the surface of the skin, can cause it to burn. The entry of current into the region of the heart or the respiratory center of the brain can lead to death. High-frequency radio emission from ball lightning occurs in the wavelength range of 1-10 cm and can be absorbed by liquid water. When ball lightning comes into close contact with the body, blood heating and muscle rupture can occur. Cases of the indicated action of ball lightning on people are given. It is shown that the charge of ball lightning can be kept in a shell consisting of polarized water molecules. The reason for the generation of electromagnetic radiation of ball lightning is the cyclic movement of electrons in closed orbits. The radiation power sharply increases when the uniform distribution of electrons along the orbit is violated. It had been proven that dashed traces that appear on photographic films during electrical discharges in water are created by the action of multiply charged clusters having the structure of ball lightning. These clusters can penetrate the skin into living organisms and remain in them for a long time. The biological effect of these clusters has not yet been studied, but there is evidence that they are hazardous to health (causing cancer and liver damage).

Effects of High Voltage Electrical Discharge (HVED) on Endogenous Hormone and Polyphenol Profile in Wheat.

High voltage electrical discharge (HVED) is an eco-friendly low-cost method based on the creation of plasma-activated water (PAW) through the release of electrical discharge in water which results in the formation of reactive particles. Recent studies have reported that such novel plasma technologies promote germination and growth but their hormonal and metabolic background is still not known. In the present work, the HVED-induced hormonal and metabolic changes were studied during the germination of wheat seedlings. Hormonal changes including abscisic acid (ABA), gibberellic acids (GAs), indol acetic acid (IAA) and jasmonic acid (JA) and the polyphenol responses were detected in the early (2nd day) and late (5th day) germination phases of wheat as well as their redistribution in shoot and root. HVED treatment significantly stimulated germination and growth both in the shoot and root. The root early response to HVED involved the upregulation of ABA and increased phaseic and ferulic acid content, while the active form of gibberellic acid (GA1) was downregulated. In the later phase (5th day of germination), HVED had a stimulatory effect on the production of benzoic and salicylic acid. The shoot showed a different response: HVED induced the synthesis of JA_Le_Ile, an active form of JA, and provoked the biosynthesis of cinnamic, p-coumaric and caffeic acid in both phases of germination. Surprisingly, in 2-day-old shoots, HVED decreased the GA20 levels, being intermediate in the synthesis of bioactive gibberellins. These HVED-provoked metabolic changes indicated a stress-related response that could contribute to germination in wheat.

Study on Townsend first ionization coefficient in a streamer filament of the pulsed electric discharge in water

Streamers in water usually consist of several weakly ionized gaseous filaments. It is important to understand the ionization and excitation processes occurring in a streamer filament. In this paper, we studied the Townsend first ionization coefficient α in a streamer filament. The emission images of streamers in water were acquired by using an ultra-high speed camera system. Based on the emission images, it was found that the luminance of a streamer filament decreased exponentially as the distance increased from the anode tip. The Townsend first ionization coefficient in the streamer filament in water was then estimated by the emission profile method. It was found that the Townsend first ionization coefficient in a streamer filament was 5.3 cm−1 on average and did not depend on the water conductivity or the applied voltage of interest in the present paper. The Townsend first ionization coefficient estimated by the emission profile method is in agreement with that deduced from the electron density profile of the streamer filament in water, indicating that the emission profile method for measuring the Townsend first ionization coefficient can be applicable to the streamers in water. We also estimated the reduced Townsend first ionization coefficient α/N in a streamer filament in water and found that the obtained value for α/N was four orders of magnitude lower than those obtained from the glow discharge in low pressure water vapor, but at least ten orders of magnitude greater than those predicted by the empirical formulas.

Electrode Erosion During High-Voltage Electrical Discharge in a Liquid

The paper presents the results of experimental studies of the mass value of electrode (anode) erosion during a high-voltage electric discharge in a liquid. The results obtained made it possible to determine the influence of technological parameters and operating conditions of high-voltage electric discharge installations on the mass erosion of an anode. It is noted that with an increase in the specific electrical conductivity of the working fluid and in the length of the interelectrode gap, a decrease in the value of the mass erosion of the anode is observed. Comparison of mass erosion of anodes made of copper, steel, and aluminum showed that among them the steel anode has the highest erosion resistance during an electric discharge in water. Based on the results of the performed experimental studies, an empirical technique was developed that allows to estimate the mass erosion of the anode in one electric discharge in water.

Simulation of Electrooptical Measurements of Prebreakdown Electric Fields in Water—Part I: Electric Field Near Anode Streamer

The analysis of the results of electrooptical measurements using the Kerr effect at the prebreakdown stage of an electric discharge in water made it possible to estimate the intensity of the inception field of the anode streamer. The electric field strength and phase difference distribution were constructed using computer simulation in the point-to-plane system near the anode tip. The conditions of an actual experiment are simulated. It turned out that taking into account the nonlinearity of the relative permittivity and saturation of polarization leads to a sharp increase in the field strength in a narrow region near the needle tip and compression of both the strong field region and compression of Kerr fringes. Taking these factors into account made it possible to explain the unusual shape of the chronogram and to estimate the field strength of the appearance of the anode streamer as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula> ~ 40–50 MV/cm.

Influence of the Volume of a Cylindrical Discharge Chamber with Rigid Walls on the Pressure Field in the Water Filling It

The volume of the discharge chamber has a great influence on the pressure field in the water filling it and on the efficiency of many technological processes; therefore, the study of the relationship between the volume of the chamber and the pressure in it is an urgent task. However, at present, the role of the volume of the discharge chamber in the formation of the pressure field in it has been insufficiently studied. The purpose of this work is to fill the gap. The study was carried out on the base of a previously developed mathematical model of an electric discharge in water, the adequacy of which was substantiated via a comparison of the simulation results with experimental data. It is determined that the closed volume of the discharge chamber with rigid walls significantly affects the formation of the pressure field in the water filling it. In this case, the interaction of waves reflected from the walls of the discharge chamber with the surface of the discharge channel in water and the vapor-gas cavity is of decisive importance. The reflected waves determine the period and amplitude of the pulsation of the discharge channel and the vapor-gas cavity, thereby influencing the electrical characteristics of the discharge. This influence increases with decreasing the chamber volume.

Pulsed high-voltage electrical discharges in water: The resource for hydrogen production and water purification

The high-voltage electrical pulses with magnitude up to 200 kV, generated in water, are studied experimentally. These pulses are the water sample saturation result by less powerful pulses with magnitude of 10 kV and higher frequency. The pulse generation process is accompanied by release of hydrogen from water into environment. Besides, the considered complex of two dischargers generates electricity, the power of which exceeds the input power. Proposed the hypothetical mechanism of the process based on successive acts of acceleration and thermalization of protons. The results of wastewater treatment by generated high-voltage pulses are also presented.

Microsecond Electrical Breakdown in Water: Advances Using Emission Analysis and Cavitation Bubble Theory.

Electrical discharges in water are a subject of major interest because of both the wide range of potential applications and the complexity of the processes. This paper aimed to provide significant insights to better understand processes involved during a microsecond electrical discharge in water, especially during the propagation and the breakdown phases. Two different approaches were considered. The first analysis focused on the emission produced by the discharge during the propagation using fast imaging measurements and spatially resolved optical emission spectroscopy. The excited species H, O, and OH were monitored in the whole interelectrode gap. The second analysis concerned the thermodynamic conditions induced by the breakdown of the discharge. The time evolution of the bubble radius was simulated and estimation of the initial pressure of the cavitation bubble was performed using the Rayleigh–Plesset model. Values of about 1.7 × 107 Pa and 1.2 × 108 Pa were reported for the cathode and anode regimes, respectively. This multidisciplinary approach constitutes a new step to obtain an accurate physical and chemical description of pin-to-pin electrical discharges in water.

Re-illumination and pause behavior of streamer filament of streamer discharge in water

The streamer discharge in water is a main object for studying the basic physical and chemical processes of an electric discharge in water. In this paper, the re-illuminations and the pause behaviors of a streamer filament of the microsecond pulsed streamer discharge in water with different conductivities (20 to 800 µS/cm) are studied by adopting a needle-plate electrode system and an ultra-high-speed camera system. The cause why the re-illumination of the streamer filament is difficult to detect by using the camera system as the water conductivity gets higher is discussed. It is found that the re-illumination alternately occurs among different streamer filaments, and two modes of the re-illumination are identified: one is that the whole filament quenches and then illuminates again; the other is that only the tip part of the filament quenches and then resumes the illumination. The appearance rate of the re-illumination of the streamer filament decreases rapidly as the water conductivity increases, and then drops to zero as the water conductivity exceeds 540 µS/cm. Within a water conductivity range of 20–800 µS/cm, the appearance rate of segmentation in shockwave pattern of the streamer filament is larger than 65%, indicating that the pause is a common behavior of the streamer filament. By measuring the difference in radius between two adjacent shockwave segments, the average pause period of the streamer filament is estimated at 157 ns, which is almost not affected by the water conductivity. As the water conductivity increases, the light intensity of the streamer filament increases rapidly. The light intensity of the streamer filament cannot decay to the noise level of the camera system during the pause period of the streamer filament as the water conductivity exceeds 350 µS/cm. The streamer filament produces glow on the light emission image, which makes it difficult to distinguish the “extinction and illumination” process by the camera system.

Comparative Analysis of Methods for Mathematical Modeling of Specific Electrical Conductivity of Plasma in the Channel of an Electric Discharge in Water

In the present work, a comparative analysis of three methods for determining the specific electrical conductivity of the plasma formed in the channel of an electric discharge in water is carried out for its mathematical modeling. The parameters of the empirical function are determined, at which the results of mathematical modeling are consistent with the experimental data. The necessity of using empirical functions in calculating the specific electrical conductivity of plasma has been substantiated. The obtained ratios made it possible to significantly increase the adequacy of the previously developed mathematical model of the physical discharge processes in water and to expand the range of parameters in which it can be used.

Influence of Vapor-Gas Cavity on Pressure Field in Closed Discharge Chamber with Rigid Walls

The pressure field in discharge chambers of a limited volume with deformable walls very often has a great influence on the efficiency of technological processes of deformation of sheet alloys; therefore, its determination is an urgent task. As a result of an electric discharge in the liquid filling the discharge chamber, in it, a cavity with a higher compressibility is formed than the liquid in the chamber. At the stage of the discharge, this cavity is filled with non-ideal plasma, and after the discharge, with liquid vapor and gases dissolved in it (vapor-gas cavity). Its pulsations form a pressure field in the discharge chamber. The moving boundary of the vapor-gas cavity creates great problems in calculating the pressure field in a liquid, especially after a large number of its pulsations. At present, the role of the vapor-gas cavity in the formation of the pressure field in the discharge chamber with a deformable wall, which is a sheet alloy plate, is insufficiently studied. Its definition is the purpose of this work. The study was carried out on the base of a previously developed mathematical model of an electric discharge in water, which in this work is supplemented with relations that significantly increase the accuracy of calculating the resistance of the discharge channel and the energy released in it. It was determined that the pulsations of the vapor-gas cavity provide pressure fluctuations in it in an antiphase with the average pressure in the liquid. In a discharge chamber with rigid walls, they decay slowly, but the presence of a deformable wall leads to a rapid decay of pressure fluctuations. In the previously developed mathematical model, the change in the optical transparency of the plasma was taken into account, and its significant effect on the pressure in the cavity and the pressure field in the liquid was determined.

Atomic scale microscopy unveils the growth mechanism of 2D-like CuO nanoparticle agglomerates produced via electrical discharges in water

In this paper we describe the growth mechanism leading to the selective synthesis of 2D-like CuO nanoparticle agglomerates via pulsed electrical discharges in water. By adjusting the voltage and pulse width, we selected four experimental conditions: 5 kV/100 ns, 5 kV/500 ns, 20 kV/100 ns and 20 kV/500 ns. In these conditions, we obtained agglomerates with dimensions ranging between 40 and 100 nm, formed of CuO nanoparticles having sizes of few nm. While the morphology of the agglomerates and their composition do not change in all the four conditions, the size, the shape and the crystal properties of the CuO nanoparticles can be finely tuned by choosing the coupling between voltage and pulse width. Moreover, the nanoparticles are more densely agglomerated at longer pulse width. Based on our observations, we infer the growth mechanism of the CuO nanoparticle agglomerates. We demonstrate that CuO nanoparticles are formed during the discharge, while their agglomeration can be mainly due to the pressure gradients existing within the plasma formed by the discharge, which encourage nanoparticle agglomeration on one plane.

Method for Initial Conditions’ Determination to Model Electric Discharge in Water

The problem of determining initial conditions to ensure the uniqueness of the mathematical modeling of the electric discharge in water was formulated and solved. The method was developed for determining initial values of the discharge characteristics, which ensure their agreement between each other. The method efficiency was exhibited by the example of the electric discharge in water, whose experimental data are known. The effect of the arbitrary parameters of the electric discharge system on the mathematical modeling results was defined. The performed studies made it possible to substantially enhance the adequacy of the mathematical model developed earlier to the processes of the discharge in water at its initial stage.

Statistical analysis of a micro-pulsed electrical discharge in water

This paper reports the statistical analysis of three electrical parameters (breakdown voltage Ubk, current peak Ipk, breakdown duration τbk) for a pin-to-pin micro-pulsed discharge in water. Two complementary plots, Ubk = f(Ipk) and Ipk = f(τbk), have been used to identify four different regimes of discharge in water (cathode, anode, mixed and double) and a linear correlation has been shown between the breakdown voltage and the current peak. Moreover, this paper demonstrates that the measurements of the three electrical parameters follow normal distributions. As a consequence, the mean value and the standard deviation provide valuable information in order to perform parametric studies. Such an investigation has been carried out considering a large range of solution conductivities from 2 µS cm−1 to 1500 µS cm−1, and the analysis of the propagation mechanisms of the discharge has been discussed.

Mathematical Modeling of Change in Plasma’s Specific Electrical Conductivity and Noncylindrical Channel Resistance during the Process of Electrical Discharge in Water

This work formulated and solved the problem of determining the specific electrical conductivity of plasma in the channel of the electrical discharge in water as well as that of the discharge channel resistance taking into account the deviation in its shape from that of a straight circular cylinder. The closing ratios and empirical functions whose parameters agree with the experimental data are obtained. The use of the empirical functions necessary for the calculation of the specific electrical conductivity of plasma is justified in connection with its high nonideality and relatively low degree of ionization. The obtained relations allowed for substantially increasing the adequacy of the mathematical model developed earlier for the physical processes of the discharge in water and expanding the range of parameters in which it can be applied.

Synthesis of copper and copper oxide nanomaterials by electrical discharges in water with various electrical conductivities

In the present study, Cu-based nanomaterials are synthesized by initiating spark discharges between two copper electrodes immersed in de-ionized water. The electrical conductivity of water is varied by adding HCl at very low concentrations. The discharge and water properties are determined by measuring the current-voltage waveforms and monitoring water acidity and conductivity, respectively. Scanning electron and transmission electron microscopy analyses of the produced nanoparticles show that increasing water conductivity, by adding HCl, promotes the synthesis of Cu-based nanomaterials. Depending on the initial water conductivity, various nanostructures are observed, including nanoflakes of cuprite (Cu2O), dendrites with high Cu content, and unordered micrometric aggregates with a mixed Cu/Cu2O content. The initial water conductivity also affects the chemical structure, mainly the relative Cu/Cu2O crystalline content.

Shockwaves from pulsed streamer discharge imaged at ultra-high speeds

A high-speed camera system revealed the individual shockwaves created by a pulsed electrical discharge in water, unveiling some of the fundamental physics.