The term plasma actuator has now been a part of the fluid dynamics flow-control vernacular for more than a decade. A particular type of plasma actuator that has gained wide use is based on a single–dielectric barrier discharge (SDBD) mechanism that has desirable features for use in air at atmospheric pressures. For these actuators, the mechanism of flow control is through a generated body-force vector field that couples with the momentum in the external flow. The body force can be derived from first principles, and the effect of plasma actuators can be easily incorporated into flow solvers so that their placement and operation can be optimized. They have been used in a wide range of internal and external flow applications. Although initially considered useful only at low speeds, plasma actuators are effective in a number of applications at high subsonic, transonic, and supersonic Mach numbers, owing largely to more optimized actuator designs that were developed through better understanding and modeling of...

Dielectric Barrier Discharge Plasma Actuators for Flow Control

Dielectric Barrier Discharges (DBDs) are plasmas generated in configurations with an insulating (dielectric) material between the electrodes which is responsible for a self-pulsing operation. DBDs are a typical example of nonthermal atmospheric or normal pressure gas discharges. Initially used for the generation of ozone, they have opened up many other fields of application. Therefore DBDs are a relevant tool in current plasma technology as well as an object for fundamental studies. Another motivation for further research is the fact, that so-called partial discharges in insulated high voltage systems are special types of DBDs. The breakdown processes, the formation of structures, and the role of surface processes are currently under investigation. This review is intended to give an update to the already existing literature on DBDs considering the research and development within the last two decades. The main principles and different modes of discharge generation are summarized. A collection of known as well as special electrode configurations and reactor designs will be presented. This shall demonstrate the different and broad possibilities, but also the similarities and common aspects of devices for different fields of applications explored within the last years. The main part is devoted to the progress on the investigation of different aspects of breakdown and plasma formation with the focus on single filaments or microdischarges. This includes a summary of the current knowledge on the electrical characterization of filamentary DBDs. In particular, the recent new insights on the elementary volume and surface memory mechanisms in these discharges will be discussed. An outlook for the forthcoming challenges on research and development will be given. Page 1 of 47 AUTHOR SUBMITTED MANUSCRIPT PSST-101368.R1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A cc ep e M nu sc rip t Progress on DBD Sources and Filaments 2

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Dielectric barrier discharges: progress on plasma sources and on the understanding of regimes and single filaments

The term “plasma actuator” has been a part of the fluid dynamics flow control vernacular for more than a decade. A particular type of plasma actuator that has gained wide use is based on a single dielectric barrier discharge (SDBD) mechanism that has desirable features for use in air at atmospheric pressures. For these actuators, the mechanism of flow control is through a generated body force vector that couples with the momentum in the external flow. The body force can be derived from first principles and the plasma actuator effect can be easily incorporated into flow solvers so that their placement and operation can be optimized. They have been used in a wide range of applications that include bluff body wake control; lift augmentation and separation control on a variety of lifting surfaces ranging from fixed wings with various degrees of sweep, wind turbine rotors and pitching airfoils simulating helicopter rotors; flow separation and tip-casing clearance flow control to reduce losses in turbines, to control flow surge and stall in compressors; and in exciting instabilities in boundary layers at subsonic to supersonic Mach numbers for turbulent transition control. New applications continue to appear through programs in a growing number of US universities and government laboratories, as well as in Germany, France, England, Netherland, Russia, Japan and China. This paper provides an overview of the physics, design and modeling of SDBD plasma actuators. It then presents their use in a number of applications that includes both numerical flow simulations and experiments together.

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Single dielectric barrier discharge plasma enhanced aerodynamics: physics, modeling and applications

Over the last ten years, expansion of atmospheric pressure plasma solutions for surface treatment of materials has been remarkable, however direct plasma technology for thin film deposition needs still great effort. The objective of this paper is to establish the state of the art on scientific and technologic locks, which have to be opened to consider direct atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) a viable option for industrial application. Basic scientific principles to understand and optimize an AP-PECVD process are summarized. Laboratory reactor configurations are reviewed. Reference points for the design and use of AP-PECVD reactors according to the desired thin film properties are given. Finally, solutions to avoid powder formation and to increase the thin film growth rate are discussed.

Atmospheric Pressure Low Temperature Direct Plasma Technology: Status and Challenges for Thin Film Deposition

This paper is a state of the art of the understanding on the physics of homogeneous dielectric barrier discharge at atmospheric pressure. It is based on the analysis of present and previous work about the behavior of these discharges and the conditions to get them. Mechanisms controlling the homogeneity during gas breakdown and discharge development are successively discussed. The breakdown has to be a Townsend one, the ionization has to be slow enough to avoid a large avalanche development. During the breakdown, the discharge homogeneity is related to the ratio of the secondary emission at the cathode (γ coefficient) on the ionization in the gas bulk (α coefficient). Higher is this ratio, higher is the pressure × gas gap product (P.d.) value for which a Townsend breakdown is obtained. Among the phenomena enhancing the secondary emission there is the negative charge of the dielectric on the cathode surface, the trapping of ions in the gas and the existence of excited state having a long lifetime compared to the time between two consecutive discharges. The first phenomenon is always present when the electrodes are covered by a solid dielectric, the second one is related to the formation of a positive column and the third one is specific of the gas. During the discharge development, the homogeneity is mainly controlled by the voltage or the current imposed by the electrical circuit /electrode configuration and to the gas ability to be slowly ionized. Larger is the contribution of a multiple step ionization process like Penning ionization, higher will be the working domain of the discharge. A decrease of the gas voltage during the discharge development is a solution to enhance the contribution of this process. After 20 years of research a lot of mechanisms have been understood however there is still open questions like the nature of the Inhibited homogeneous DBD, surface energy transfers, role of attachment and detachment…

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Recent advances in the understanding of homogeneous dielectric barrier discharges

This work is a contribution to the understanding of the mechanisms controlling the transition from a Townsend to a filamentary dielectric barrier discharge when the power increases. The approach consists in developing an electrical model of the discharge and the power supply to study the interaction between these two elements. The main components of the discharge model are (i) two Zener diodes whose characteristics depend on the power to take into account the effect of the gas density variation induced by the temperature variation and (ii) a RC circuit describing the memory effect from one discharge to the following one which is due to the metastables and the electrons trapped on the surface of the solid dielectrics. The calculated and measured currents are very similar over all the range of amplitude and frequency allowing to get an atmospheric pressure Townsend discharge. The model also describes the transition to filamentary discharge observed when the excitation frequency increases too much showing that it is due to a very fast variation of the load connected to the power supply. From this understanding, a solution is deduced to increase the maximum power dissipated in the discharge which consists in decreasing the solid dielectric capacitance.

https://iopscience.iop.org/article/10.1088/0022-3727/38/4/004/pdf

Electrical model and analysis of the transition from an atmospheric pressure Townsend discharge to a filamentary discharge

The aim of this paper is the modeling of a dielectric barrier discharge at atmospheric pressure, in the Townsend regime. This model is based on an equivalent electrical circuit. It takes into account the main physical phenomena of the discharge. This model allows to have a general view of the process and to study the influence of the power supply on the discharge. It is also an interesting tool for the power supply design and the process optimization.

Electrical model of an atmospheric pressure Townsend-like discharge (APTD)

Electrical model of an Atmospheric Pressure Townsend-like Discharge (APTD): application to the determination of the gas temperature

This work is a contribution to the understanding of mechanisms controlling the Atmospheric Pressure Glow Discharge (APGD). The approach consists in developing an electrical model of the discharge based on electrical circuit compounds. This model takes into account the main phenomena of the discharge including the memory effect and the creation of the cathode fall. It allows to have a general view of the process and can be easily associated to the power supply with short computational duration; it is also an interesting tool for the optimization of the whole process.

J. P. Cambronne

Papers

Electrical model and analysis of the transition from an atmospheric pressure Townsend discharge to a filamentary discharge

Electrical model of an atmospheric pressure Townsend-like discharge (APTD)

Electrical model of an Atmospheric Pressure Townsend-like Discharge (APTD): application to the determination of the gas temperature

Electrical model of the atmospheric pressure glow discharge (APGD) in helium