Abstract
This work reveals essential details of plasma-surface interaction in atmospheric air that are important for a wide range of applications, beginning from airflow control and up to the high-voltage insulation. The paper discusses experimental data characterizing dynamics of development and kinetics of energy coupling in surface dielectric barrier discharge (SDBD), atmospheric air plasmas sustained over dielectric surfaces, over a wide range of time scales. The experiments have been conducted using microsecond pulse voltage waveform of single and alternating polarities. Time-resolved discharge development and mechanisms of coupling with quiescent air are analyzed using nanosecond gate camera imaging, electrical measurements, and original surface charge sensors. The results demonstrate several new, critically important processes overlooked in previous studies. Specifically, it is shown that SDBD plasmas energy release may be significantly increased by using an optimized waveform.
Highlights
Beginning from early experiments [1]-[3], the analysis of mechanisms of a boundary-layer transition and separation control using surface dielectric barrier discharge (SDBD) actuators continues to be one of the main trends in active flow control studies
There appears to be little difference in the physical processes between these time scales. This variance in time scale may be apparent in the dynamics of interaction with high-speed flow
The time scales discussed in this paper (>10 μs) are higher than a characteristic gas dynamic time in high-speed flow (~10 μs) whereas previous works are on a scale smaller (~10 - 100 ns) than this
Summary
Beginning from early experiments [1]-[3], the analysis of mechanisms of a boundary-layer transition and separation control using surface dielectric barrier discharge (SDBD) actuators continues to be one of the main trends in active flow control studies. The increase of flow control authority is limited by surface charge accumulation, which reduces the electric field in the plasma It is limited by the ionization instability appearing in the form of discharge contraction (constriction in some papers), potentially making localized Joule heating a more significant effect. Several papers [11] [13]-[15] consider the compression waves generated in nanosecond pulse DBD plasma actuators due to mechanism of fast heating [16] [17] as the major agent of the plasma control effect In spite of these detailed studies, there appears to be no direct evidence that compression waves generated by heating on sub-acoustic time scale are the dominant factor in boundary layer tripping or generation of coherent flow structures. It was demonstrated that discharge contraction results in a significant increase of energy stored on the dielectric surface during and after the NS discharge pulse, which in this case greatly exceeds energy dissipated as Joule heat (up to a factor of 3 - 4)
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