Active flow control is a topic in full expansion due to associated industrial applications of huge importance, particularly for aeronautics. Among all flow control methods, such as the use of mechanical flaps, wall synthetic jets or MEMS, plasma-based devices are very promising. The main advantages of such systems are their robustness, simplicity, low power consumption and ability for real-time control at high frequency. This paper is a review of the worldwide works on this topic, from its origin to the present. It is divided into two main parts. The first one is dedicated to the recent knowledge concerning the electric wind induced by surface non-thermal plasma actuators, acting in air at atmospheric pressure. Typically, it can reach 8 m s−1 at a distance of 0.5 mm from the wall. In the second part, works concerning active airflow control by these plasma actuators are presented. Very efficient results have been obtained for low-velocity subsonic airflows (typically U∞ ≤ 30 m s−1 and Reynolds number of a few 105), and promising results at higher velocities indicate that plasma actuators could be used in aeronautics.

https://iopscience.iop.org/article/10.1088/0022-3727/40/3/S01/pdf

Airflow control by non-thermal plasma actuators

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 present paper is a wide review on AC surface dielectric barrier discharge (DBD) actuators applied to airflow control. Both electrical and mechanical characteristics of surface DBD are presented and discussed. The first half of the present paper gives the last results concerning typical single plate-to-plate surface DBDs supplied by a sine high voltage. The discharge current, the plasma extension and its morphology are firstly analyzed. Then, time-averaged and time-resolved measurements of the produced electrohydrodynamic force and of the resulting electric wind are commented. The second half of the paper concerns a partial list of approaches having demonstrated a significant modification in the discharge behavior and an increasing of its mechanical performances. Typically, single DBDs can produce mean force and electric wind velocity up to 1 mN/W and 7 m/s, respectively. With multi-DBD designs, velocity up to 11 m/s has been measured and force up to 350 mN/m.

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Electrical and mechanical characteristics of surface AC dielectric barrier discharge plasma actuators applied to airflow control

Cold atmospheric plasma: Sources, processes, and applications

The electrical properties of an asymmetric surface dielectric barrier discharge in atmospheric air have been investigated experimentally. The discharge is used for airflow production close to the dielectric surface, and the time-averaged flow velocity spatial profiles have been measured. Velocities of up to 3.5 m s−1 at heights of 1–2 mm are reached when filamentary discharges with current peaks up to 20 mA are produced along the surface. In terms of powers, mechanical powers (output) of a few milliwatts are obtained for electrical powers (input) up to 10 W. Variation laws or behaviour with several discharge parameters (applied voltage waveform, distance between electrodes, dielectric thickness and permittivity) have been experimentally determined.

https://iopscience.iop.org/article/10.1088/0022-3727/38/19/012/pdf

Asymmetric surface dielectric barrier discharge in air at atmospheric pressure: electrical properties and induced airflow characteristics

A transparent plasma discharge reactor using air was used to investigate the transition from a filamentary dielectric barrier discharge (FDBD) operation regime into the diffuse barrier discharge regime. Recent results of other researchers indicate that the stability of diffuse barrier discharges in nitrogen may be attributed to the lack of a fully formed cathode fall layer when the discharge operates in a regime between the Townsend discharge and a normal glow discharge. We have demonstrated that a diffuse barrier discharge in air exhibits an increased accumulation of electric charge on the electrode's dielectric plates as compared with the FDBD. This may provide a means of stabilizing the discharge in a Townsend-to-glow discharge transition. Unlike operation in nitrogen, a streamer mechanism is involved in the formation of a uniform air plasma, though in a different manner than is associated with the FDBD. Numerous diffuse streamer clusters were observed on pre-charged dielectric plates at the breakdown voltage. Our conclusion is that the macroscopically uniform atmospheric-pressure DBD in air is obtained by the numerous radially expanding streamers that are temporally overlapping.

https://iopscience.iop.org/article/10.1088/0022-3727/38/4/006/pdf

The transition from a filamentary dielectric barrier discharge to a diffuse barrier discharge in air at atmospheric pressure

The Physics and Phenomenology of Paraelectric One Atmosphere Uniform Glow Discharge Plasma (OAUGDP) Actuators for Aerodynamic Flow Control

Summary form only given, as follows. The one atmosphere uniform glow discharge plasma (OAUGDP) is capable of operating at one atmosphere in air and other gases, and its active species can be used for the plasma treatment of surfaces. The OAUGDP can he operated in a wide range of geometrical configurations, ranging from a slab plasma between parallel plates, to a plasma layer which can cover an isolated flat or curved surface. The remote exposure reactor (RER) utilizes multiple flat panels covered with a surface layer of OAUGD plasma to generate active species from air, which have been convected distances of 20 cm or more downstream of the last plasma. These active species are capable of sterilizing the surface of materials. Our investigations have shown that the energizing voltage, the RF frequency, the RF power input, the number of panels generating the surface layers of the OAUGDP, and the distance active species are convected from the plasma panels to the workpiece all affect the killing times of microorganisms and other plasma processing effects. The relative concentration of active species in the efflux of the remote exposure reactor is determined by mass spectrometry and reported as a function of the above plasma parameters and the distance from the last plasma generating panel. Such information will be correlated with plasma sterilization data from the RER to learn more about the agents responsible for sterilization.

Daniel M Sherman

Papers

The transition from a filamentary dielectric barrier discharge to a diffuse barrier discharge in air at atmospheric pressure

The Physics and Phenomenology of Paraelectric One Atmosphere Uniform Glow Discharge Plasma (OAUGDP) Actuators for Aerodynamic Flow Control

Mass spectrometry of active species convected from a one atmosphere uniform glow discharge plasma (OAUGDP) in air