Plasma Diagnostics and Modelling of Nanosecond Pulsed Surface Dielectric Barrier Discharge Actuators

During the past years, an increasing number of studies have been conducted on the use of electrical discharges for the stabilization of airflows (plasma flow control). Electrical gas discharges transfer energy and momentum to the gas through collisions of free electrons with atoms and molecules. Chemically active species such as ions, radicals and excited species are produced due to these collisions. The use of plasma actuators, notably surface dielectric barrier discharges (SDBD), for flow control applications has been largely investigated, and it has been demonstrated to effectively control the flow at low flow speed (below 30 m/s). Nowadays, the research in this area focuses on ways to improve the plasma actuators for flow speeds relevant to real flight conditions. One promising device for plasma flow control at high flow speed is the nanosecond pulsed surface dielectric barrier discharge. Nanosecond pulsed plasmas in general have also drawn attention from other fields, such as plasma assisted combustion, due to their ability to produce a large amount of active species and producing substantial overheating in a very short time. In this thesis an investigation of nanosecond pulsed SDBD is presented, with a focus on flow-control applications, but also on the production of active species, which are of great interest for plasma-assisted combustion and for other fields. The experimental characterization of the plasma created for different conditions, such as the operating pressure, the polarity and the amplitude of the applied voltage, is conducted. Important plasma parameters such as the gas temperature, the excited species produced, the reduced electric field or the electron density are either directly measured or inferred from emission spectroscopy using existing and novel diagnostic methods. The validity of the diagnostic methods is demonstrated using a numerical model of the plasma. The numerical modelling of the plasma also allows determining the influence of the plasma on the flow for several conditions. The experimentally studied conditions are simulated and compared with experimental results to show the strengths and limitations of the numerical model.

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