PLASMA FOR FLOW AND NOISE CONTROL
Atmospheric pressure cold plasma discharges are an interesting alternative to low pressure plasmas, since the possibility of avoiding the use of vacuum systems favours the technological transfer of promising plasma processes.
Among different kinds of sources, Dielectric Barrier Discharges (DBDs) are outstanding for their versatility and for the setup simplicity. The main feature consists in the insertion of a dielectric layer within the discharge gap in order to insulate at least one of the two electrodes. Three examples of plane and quite standard configurations are depicted in the following figure, where the electrodes are shown in blue, the insulating material in green and plasma in violet.
When plasma is created ionizing just a thin sheet of plasma nearby the dielectric surface and one electrode we talk of Surface Dielectric Barrier Discharge (SDBD). This can be achieved using the configuration shown in next figure. In SDBDs, when a sufficiently high voltage is applied between the electrodes and the plasma sheet is created, a “plasma induced airflow” of several metres per second is created in the black arrow direction. This flow can favourably interact with an external wind flowing nearby the DBD dielectric surface, making these discharges interesting for aerodynamic applications. SDBDs are thus often referred to as “plasma actuators”.
Over the last decade, plasma control of airflows along surfaces has been the subject of many experimental studies whose aim was to reduce turbulence, to decrease drag, to enhance airfoil lift or to prevent flow detachment. It is evident that the aeronautical sector can take many benefits from the application of the so called plasma actuators. However, the growing interest for these devices is also due to the environmental benefits they can deal to. As a matter of fact, apart from the fact that drag reduction can result in fuel and thus pollution reduction, it is known that the problem of acoustic pollution affecting an airport neighbourhood is mainly due to the airflow detachment occurring in correspondence of an aircraft bluff body (such as a landing gear).
The presence of an insulating layer interposed between electrodes prevents the formation of a diffuse plasma, inducing electrical discharges to assume the form of intermittent, fast (tens of nanoseconds) and localized (submillimetric) channels where current flows, generally called “plasma microdischarges”.
At PlasmaPrometeo these plasma are studied and characterized with optical and electrical diagnostics: due to the short temporal and the small spatial scales involved, the SDBD regime and properties are not completely understood yet. Moreover, these investigations are required in order to get better and better aerodynamic results and to understand which parameters mainly affect plasma actuator performances. At this purpose, PlasmaPrometeo has collaborations with the aircraft industry.
» Further information is available in papers published in scientific reviews:
 Biganzoli,; Barni,; Riccardi, Temporal evolution of a surface dielectric barrier discharge for different groups of plasma microdischarges, Journal of physics. D, Applied physics, 46 (2), pp. 025201 – 025211, 2013, ISSN: 0022-3727.
 Biganzoli,; Barni,; Riccardi, On the use of Rogowski coils as current probes for atmospheric pressure dielectric barrier discharges, Review of scientific instruments, 84, pp. 016101.1 – 016101.3, 2013, ISSN: 0034-6748.
 Biganzoli,; Barni,; Riccardi,; Gurioli,; Pertile, Optical and Electrical Characterization of a Surface Dielectric Barrier Discharge Plasma Actuator, Plasma sources science & technology, 22, pp. 025009.1 – 025009.9, 2013, ISSN: 0963-0252.
 Biganzoli, Barni, Riccardi, Properties of Atmospheric Pressure Microdischarges in a Surface Dielectric Barrier Device, European Conference Abstract, 36F, P5.162, 2012
 Barni, Biganzoli, Riccardi, Experimental characterization of plasmas for aerodynamical applications, Proceedings of the 30th ICPIG Conference (Belfast: Queen’s University), D16-213, 2012