Electric field distribution in a surface plasma flow actuator powered by ns discharge pulse trains

Abstract

Electric field vector components in a nanosecond pulse, surface dialectric barrier discharge plasma actuator are measured by picosecond second harmonic generation, for positive, negative, and alternating polarity pulse trains. Plasma images show that in the same polarity train, the positive polarity discharge develops as two consecutive surface ionization waves, while the negative polarity discharge propagates as a single diffuse ionization wave. In the alternating polarity train, both positive and negative polarity discharge plasmas become strongly filamentary. In all pulse trains, the measurement results demonstrate a significant electric field offset before the discharge pulse, due to the surface charge accumulation during previous discharges pulses. This demonstrates that charge accumulation is a significant factor affecting the electric field in the discharge, even at very low pulse repetition rates. Peak electric field measured in the alternating polarity pulse train is lower compared to that in same polarity trains. However, the coupled pulse energy in the alternating polarity train is much higher, by a factor of 3-4, most likely due to the neutralization of the surface charge accumulated on the dielectric during the previous, opposite polarity pulses. This suggests that plasma surface actuators powered by alternating polarity pulse trains may generate higher amplitude thermal perturbations, producing a stronger effect on the flow field. The present results show that the time scale for the electric field reduction in the plasma after breakdown is fairly long, several tens of ns, including the conditions when the discharge develops as a diffuse ionization wave. This suggests that a considerable fraction of the energy is coupled to the plasma at a relatively low reduced electric field, several tens of Townsend. At these conditions, the discharge energy fraction thermalized as rapid heating would remain fairly low, thus limiting the effect on the flow caused by the highamplitude localized thermal perturbations.

Successively accelerated ionic wind with integrated dielectric-barrier-discharge plasma actuator for low-voltage operation

“…By contrast, in the voltage rising phase, streamer-like and diffusive discharges are observed above the grounded and high-voltage covered electrodes, respectively. These discharge structures are the same as those of discharges triggered by the nonbiased NS pulses as reported in previous experimental 30 and numerical 31 studies, indicating that the DC voltage has only a small effect on the discharge structure. The electron number density during the pulsed discharge is in the order of 10 20 m −3 (up to 10 21 m −3 at the streamer head); this value is typical of atmospheric discharge 32 .…”

The Equivalent Circuit Approach for the Electrical Diagnostics of Dielectric Barrier Discharges: The Classical Theory and Recent Developments

“…For completeness, other approaches for electrical diagnostics of DBD should be mentioned: for example, statistical methods based on detailed analysis of the shapes of the current pulses measured in a DBD driven by sinusoidal voltage [24,26,27], modeling of the discharge processes [28][29][30], the simulation of the measured characteristics by defining the properties of lumped electrical elements of the equivalent circuit in XCOS/Scilab or the Simulink environment [31][32][33][34], or optical measurements of the electric field [35][36][37] and electron densities [38,39].…”

Electric field measurements in a He:N2 nanosecond pulsed discharge with sub-ns time resolution

“…The electric field induced second harmonic generation (E-FISH) [58][59][60][61][62][63][64][65][66] is a third-order non-linear process involving an external applied electric field (in a discharge, for example), and an electric field of a light wave (laser emission). In the presence of the external electric field, the light field at frequency ω induces a dipole moment in gas molecules/atoms at the second-harmonic frequency 2ω [67]:…”