Nanosecond Discharge Processes in Liquid Water

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Chemical Processes and Systems".

Deadline for manuscript submissions: closed (31 August 2022) | Viewed by 3735

Special Issue Editors


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Guest Editor
Department of Pulsed Plasma Systems, Institute of Plasma Physics, The Czech Academy of Sciences, 18200 Prague, Czech Republic
Interests: optical and electrical diagnostics; energy transfer processes; streamer discharges

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Guest Editor
Department of Physical Electronics, Masaryk University, 61137 Brno, Czech Republic
Interests: simulations and theory related to nanosecond discharges in liquid water; streamer discharges; plasma jets and dielectric barrier discharges simulations; vibrational kinetics in N2-O2 streamer discharges; sensitivity analysis and uncertainty quantification of kinetic schemes; fluid modeling of Hall-effect thrusters

Special Issue Information

Dear Colleagues,

Electrical discharges in liquid water initiated by high-voltage pulses of (sub)nanosecond duration is a very complex phenomenon. It likely involves the disruption of the cohesion and structure of liquid water on a molecular level through the generation and multiplication of nanoruptures or nanovoids followed  by  the  production  and multiplication of charged species in a highly collisional environment. These electrostriction-driven processes may compete or be supplemented by alternative ionization processes occurring on the metal–liquid interface, such as field ionization. Ultrafast processes associated with the re-arrangement of the H-bonded liquid water matrix under the influence of a transient external electric field allow the onset and evolution of plasma filaments without the occurrence of liquid-to-gas phase transition. This makes a substantial difference between discharge systems based on (sub)ns and μs-ms high-voltage sources.

In order to find plausible interpretation of experimental observables through a consistent theory, further targeted experiments performed with extreme spatio-temporal resolutions and complemented with advanced modeling are necessary. For example, reliable experimental data on pressure fields developing during the first nanoseconds of the discharge events together with extended analysis of UV (<300 nm) and NIR (>800 nm) plasma-induced emission might help to identify the most important plasma parameters, such as the density and mean energy of electrons in plasma filaments.

Models for the dynamics of a dielectric liquid in a nonuniform pulsed electric field, the formation of discontinuities, electron multiplication, and the search for the possible sources of the primary electrons constitute basic topics of the current research. Validated models can reveal the possible physical scenarios and provide a solid testing ground in the quest for the sequence of events leading to the development of the nanosecond plasmas in liquid water.

This Special Issue on “Nanosecond Discharge Processes in Liquid Water” aims to highlight recent advances both in experiments and computational modeling addressing key issues of ultrafast plasma formation in polar liquids, namely in water.

Topics include, but are not limited to:

  • Signatures of ultrafast processes associated with plasma formation in liquid water;
  • Novel diagnostic approaches performed at a (sub)ns resolution in time and sub(μm) resolution in space;
  • Experimental fingerprints differentiating the direct breakdown in liquid from bubble-assisted breakdown (e.g., radiative and acoustic signatures, energy efficiency of discharge products);
  • Dynamics of a dielectric liquid in pulsed electric fields;
  • Nucleation theory and cavitation in pulsed electric fields;
  • Sources of primary electrons and mechanisms of electron multiplication;
  • Model weaving.

Dr. Milan Simek
Dr. Zdenek Bonaventura
Guest Editors

Manuscript Submission Information

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Keywords

  • water
  • H-bond
  • polar liquids
  • electrostriction
  • field ionization
  • bremsstrahlung
  • recombination
  • ions
  • electron multiplication
  • nucleation
  • cavitation

Published Papers (2 papers)

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Research

8 pages, 1926 KiB  
Article
Optical Emission Spectroscopy of Underwater Spark Generated by Pulse High-Voltage Discharge with Gas Bubble Assistant
by Vitaliy Stelmashuk, Vaclav Prukner, Karel Kolacek, Andrii Tuholukov, Petr Hoffer, Jaroslav Straus, Oleksandr Frolov and Vit Jirasek
Processes 2022, 10(8), 1474; https://doi.org/10.3390/pr10081474 - 27 Jul 2022
Cited by 4 | Viewed by 1701
Abstract
This paper is aimed at the investigation of the acoustic and spectral characteristics of underwater electric sparks generated between two plate electrodes, using synchronized gas bubble injection. There are two purposes served by discharge initiation in the bubble. Firstly, it creates a favorable [...] Read more.
This paper is aimed at the investigation of the acoustic and spectral characteristics of underwater electric sparks generated between two plate electrodes, using synchronized gas bubble injection. There are two purposes served by discharge initiation in the bubble. Firstly, it creates a favorable condition for electrical breakdown. Secondly, the gas bubble provides an opportunity for the direct spectroscopy of plasma light emission, avoiding water absorption. The effect of water absorption on captured spectra was studied. It was observed that the emission intensity of the Ha line and a shockwave amplitude generated by discharge strongly depend on the size of the gas bubble in the moment of the discharge initiation. It was found that the plasma in the underwater spark channel does not correspond to a source of black-body radiation. This study can be also very useful for understanding the difference between discharges produced directly in a liquid and discharges produced in gas/vapor bubbles surrounded by a liquid. Full article
(This article belongs to the Special Issue Nanosecond Discharge Processes in Liquid Water)
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6 pages, 1642 KiB  
Communication
Oscillation of Gas Density in the Gas Filament Remained by a Streamer Discharge in Water
by Xiaoqiong Wen, Yibing Zhou, Xiaodong Xue and Yuantian Yang
Processes 2021, 9(10), 1809; https://doi.org/10.3390/pr9101809 - 12 Oct 2021
Viewed by 1440
Abstract
When a streamer discharge occurs in water, several luminous plasma filaments will be created in the water during the discharge. After the discharge, these plasma filaments turn into neutral gas phase and remain in water. The gas filament remained in water is a [...] Read more.
When a streamer discharge occurs in water, several luminous plasma filaments will be created in the water during the discharge. After the discharge, these plasma filaments turn into neutral gas phase and remain in water. The gas filament remained in water is a good object for studying the basic processes involved in the streamer propagation. We investigated the evolution of the gas filaments remained in water after a streamer discharge at different experimental conditions. We recorded eight successive images during one discharge pulse. The density of gas in the gas filament and the radius of the gas filament were measured from the obtained images. We found that the radius of the gas filament and the density of gas in the gas filament are almost not influenced by the impulse voltage within the range studied. While the conductivity of water has strong effect on the radius of the gas filament and the density of gas in the gas filament. The radius of the gas filament becomes thicker and expands faster as the conductivity of water becomes larger. The density of gas in the gas filament remained in water oscillates between 400 to 800 kg/m3 with an duration of ~10 μs during the expansion period of 4–39 μs after the HV pulse starts. Both the impulse voltage and the conductivity of water do not affect the oscillation duration of the density of gas in the gas filament. Full article
(This article belongs to the Special Issue Nanosecond Discharge Processes in Liquid Water)
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