Behavior of charged and uncharged drops in high alternating tangential electric fields

Löwe, Jens-Michael; Hinrichsen, Volker; Roisman, Ilia V.

doi:10.1103/physreve.101.023102

Cited by 16 publications

(10 citation statements)

References 40 publications

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“…Possible effects of an electric field on nucleation range from nano-scale effects involving the orientation of the dipole water molecules (Yan et al (2014)) to macro-scale phenomena, such as droplet oscillation in the case of an alternating electric field (Reguera and Rubí (2003); Löwe et al (2020); Schütte and Hornfeldt (1990)). Since nucleation is a physical process which is extremely sensitive to a variety of parameters, the experimental boundary conditions must be precisely controlled in order to distinguish unambiguously the effects on nucleation.…”

Section: Discussion Of the Boundary Conditionsmentioning

confidence: 99%

“…As shown in the figure, the electric field and each of its components are then very homogeneous and almost constant inside the entire groove in the ceramic. Note that due to the characteristic time scales for charge relaxation in water, τ e = ε/γ el , which is in the range of microseconds and the electric field τ f in the range of tens of milliseconds, the water droplets on the sapphire substrate can be assumed to be perfect conductors (Löwe et al (2020)).…”

Section: Electric Field Generationmentioning

confidence: 99%

“…Not only the amplitude and frequency, but also the oscillation mode of a sessile droplet may significantly vary for varying boundary conditions, e.g. electric field strength, charge or droplet size (Löwe et al (2020)). Depending on these parameters, various oscillation modes ranging from droplet oscillation mainly parallel to the surface to oscillations perpendicular to the surface or mixed oscillation modes are possible (Löwe et al (2020); Schütte and Hornfeldt (1990)).…”

Section: Droplet Motionmentioning

confidence: 99%

“…electric field strength, charge or droplet size (Löwe et al (2020)). Depending on these parameters, various oscillation modes ranging from droplet oscillation mainly parallel to the surface to oscillations perpendicular to the surface or mixed oscillation modes are possible (Löwe et al (2020); Schütte and Hornfeldt (1990)). Each of these modes is associated with a different interaction between the moving fluid molecules and the substrate where nucleation is predominantly expected.…”

Section: Droplet Motionmentioning

confidence: 99%

“…CC BY 4.0 License. (Löwe et al (2020)). A highly charged droplet can change its oscillation frequency depending on the electric field strength and therefore, fluid motion inside the droplet, which can affect nucleation, is changed.…”

Section: Charges On Droplets and The Substratementioning

confidence: 99%

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Experimental methodology and procedure for SAPPHIRE:a Semi-automatic APParatus for High-voltage Ice nucleation REsearch

Löwe¹,

Schremb²,

Hinrichsen³

et al. 2020

Preprint

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Abstract. Ice nucleation is of great interest for various processes such as cloud formation in the scope of atmospheric research, and icing of airplanes, ships or structures. Ice nucleation research aims to improve the knowledge about the physical mechanisms and, therefore improve the safety and reliability of the applications affected by ice nucleation. Several influencing factors like liquid supercooling or contamination with nucleants, as well as external disturbances such as an electric field or surface defects affect ice nucleation. Especially for ice crystal formation in clouds and icing of high-voltage equipment, an external electric field may have a strong impact on ice nucleation. Although ice nucleation has been widely investigated for numerous conditions, the effect of an electric field on nucleation is not yet completely understood; results reported in literature are even contradictory. In the present study, an advanced experimental approach for the examination of ice nucleation in water droplets exposed to an electric field is demonstrated. It comprises a method for droplet ensemble preparation and an experimental setup, which allows observation of the droplet ensemble during its exposure to well-defined thermal and electric fields, which are both variable over a wide range. The entire approach aims at maximizing the accuracy and repeatability of the experiments in order to enable examination of even the most minor influences on ice nucleation. For that purpose, the boundary conditions the droplet sample is exposed to during the experiment are examined in particular detail using experimental and numerical methods. The methodological capabilities and accuracy have been demonstrated based on several test nucleation experiments without an electric field, indicating almost perfect repeatability.

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Section: Discussion Of the Boundary Conditionsmentioning

confidence: 99%

Section: Electric Field Generationmentioning

confidence: 99%

Section: Droplet Motionmentioning

confidence: 99%

Section: Droplet Motionmentioning

confidence: 99%

Section: Charges On Droplets and The Substratementioning

confidence: 99%

See 3 more Smart Citations

Experimental methodology and procedure for SAPPHIRE:a Semi-automatic APParatus for High-voltage Ice nucleation REsearch

Löwe¹,

Schremb²,

Hinrichsen³

et al. 2020

Preprint

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Collaborative Research on Droplet Dynamics Under Extreme Ambient Conditions

Schulte

Dreizler

Munz

et al. 2022

Fluid Mechanics and Its Applications

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A fundamental understanding of droplet dynamics is important for the prediction and optimization of technical systems involving drops and sprays. The Collaborative Research Center (CRC) SFB-TRR 75 was established in January 2010 to focus on the dynamics of basic drop processes, and in particular on processes involving extreme ambient conditions, for example near thermodynamic critical conditions, at very low temperatures, under the influence of strong electric fields, or in situations involving extreme gradients of the boundary conditions. The goal of the CRC was to gain a profound physical understanding of the essential processes, which is the basis for new analytical and numerical descriptions as well as for improved predictive capabilities. This joint initiative involved scientists at the University of Stuttgart, the TU Darmstadt, the TU Berlin, and the German Aerospace Center (DLR) in Lampoldshausen. This first chapter provides a brief overview of the overall structure of this CRC as well as a summary of some selected scientific achievements of the subprojects involved. For further details the reader is referred to the subsequent chapters of this book related to the individual subprojects.

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Mechanical and Electrical Phenomena of Droplets Under the Influence of High Electric Fields

Löwe

Kempf

Hinrichsen

2022

Fluid Mechanics and Its Applications

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High-voltage composite insulators are specially designed to withstand different environmental conditions to ensure a reliable and efficient electric power distribution and transmission. Especially, outdoor insulators are exposed to rain, snow or ice, which might significantly affect the performance of the insulators. The interaction of sessile water droplets and electric fields is investigated under various boundary conditions. Besides the general behavior of sessile droplets, namely the deformation and oscillation, the inception field strength for partial discharges is examined depending on the droplet volume, strength and frequency of the electric field and the electric charge. Particularly, the electric charge is identified to significantly affect the droplet behavior as well as the partial discharge inception field strength. In addition to ambient conditions, the impact of electric fields on ice nucleation is investigated under well-defined conditions with respect to the temperature and electric field strength. High electric field strengths are identified to significantly promote ice nucleation, especially in case of alternating and transient electric fields. Different influencing factors like the strengths, frequencies and time constants of the electric fields are investigated. Consequently, the performed experiments enhance the knowledge of the behavior of water droplets under the impact of electric fields under various conditions.

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Behavior of charged and uncharged drops in high alternating tangential electric fields

Cited by 16 publications

References 40 publications

Experimental methodology and procedure for SAPPHIRE:a Semi-automatic APParatus for High-voltage Ice nucleation REsearch

Experimental methodology and procedure for SAPPHIRE:a Semi-automatic APParatus for High-voltage Ice nucleation REsearch

Collaborative Research on Droplet Dynamics Under Extreme Ambient Conditions

Mechanical and Electrical Phenomena of Droplets Under the Influence of High Electric Fields

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