The study of flow separation control by a nanosecond pulse discharge actuator

Du, Hai; Shi, Zhiwei; Cheng, Kwang-Ting; Li, Ganniu; Ji-chun, LU; Li, Zheng; Hu, Liang

doi:10.1016/j.expthermflusci.2015.12.002

Cited by 34 publications

(10 citation statements)

References 31 publications

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“…Specifically, phased-locked PIV measurements detected formation of large-scale spanwise vortices, resulting in reattachment of the separated boundary layer over the top surface of the airfoil at a high angle of attack when the actuator is in operation [2]. These vortices have also been detected in several subsequent studies [3,6,7,9]. These results suggested that the flow control mechanism is due to the excitation of shear layer instability by high-amplitude thermal perturbations generated by the plasma actuator.…”

Section: Introductionmentioning

confidence: 71%

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

Simeni

Tang

Frederickson

et al. 2018

Plasma Sources Sci. Technol.

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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.

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Section: Introductionmentioning

confidence: 71%

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

Simeni

Tang

Frederickson

et al. 2018

Plasma Sources Sci. Technol.

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“…Du et al. 31 report that the primary effect NS-DBD actuators for separated flow control is the local thermal perturbations under the experimental conditions. The near-surface heating is introduced by plasma discharge.…”

Section: Resultsmentioning

confidence: 99%

“…At this moment, portions of vorticity arise at the leading edge. This vorticity attaches to the airfoil wall and advects downstream (shown in Figure 15 Du et al 31 report that the primary effect NS-DBD actuators for separated flow control is the local thermal perturbations under the experimental conditions. The near-surface heating is introduced by plasma discharge.…”

Section: Time-average Flow Characterizationmentioning

confidence: 99%

“…From Figure 15 (right column), we can see that after discharge, a new series of vortexes form, and advects downstream along the shear layer. The large-scale vortex structures entrain external high-momentum fluid into the shear layer, thus strengthening the mixing of the shear layer with the main flow, 31 which is beneficial to separation control and reattachment. And by those vortexes motion, the external flow is pulled down to airfoil (Figure 15, left column).…”

Section: Time-average Flow Characterizationmentioning

confidence: 99%

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On the effect of operating condition on separated-flow control by nanosecond pulse discharge actuators

Shi

Cheng

et al. 2016

Proceedings of the Institution of Mechanical Engineers, Part G:

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The surface dielectric barrier discharge plasma actuator driven by nanosecond pulses is recognized as an effective fluid actuator for flow separation control. The operation condition of nanosecond dielectric barrier discharge actuators for separated flow control still requires further study, particularly prioritizing the improvement of the effectiveness and reducing energy consumption in flow separation control implementation. In this study, experiments are conducted using a two-dimensional NASA SC(2)-0712 airfoil in a wind tunnel with a Reynolds number of 0.5 Â 10 6 (25 m/s). The pressure measurement experiments show that the location of actuators affects the efficiency of separation control. Particle image velocimetry results indicate that the most efficient location of the actuator is upstream of the separation point and near the original point of the separated shear layer. Meanwhile, the particle image velocimetry results show the vorticity attaches to the airfoil wall after discharge, which suggests that the reattachment is due to the generation of large-scale vortices. These present structures result in the mixing of the shear layer with the main flow thereby delaying separation and reattaching a separated flow. This study shows the most efficient location related to the separation point. Furthermore, it indicates the reattachment of flow is attributed to the motion of vortexes coherent structure.

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“…Concerning the control mechanism that is responsible for the large changes of the mean and temporal airflow characteristics, we can assume that it is not yet fully identified. Indeed, some researchers believe that it is a thermal effect [27][28][29][30] since others consider that the pressure wave can interact with the natural structures and instabilities of the flow [31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

Streamer propagation and pressure waves produced by a nanosecond pulsed surface sliding discharge: effect of the high-voltage electrode shape

Moreau¹,

Bayoda²,

Bénard³

2020

J. Phys. D: Appl. Phys.

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This paper aims at better understanding nanosecond sliding discharges based on a three-electrode geometry and at studying the effect of the shape of the pulsed high-voltage electrode on their electrical, optical and mechanical properties. Three different electrode shapes are considered: a typical planar electrode with a straight edge, a planar electrode with a sawtooth edge, and a wire electrode. First, we verified that the sliding discharge starts to appear when the potential difference between both air-exposed electrodes exceeds about 25 kV, corresponding to a mean electric strength (potential difference divided by the gap) a little bit higher than 6 kV cm−1, but this value differs slightly depending on the shape of the electrode. Secondly, we highlighted that the current with the wire-based discharge is slightly higher compared to the two others because the streamers are more numerous and they are more uniformly distributed along the wire. Moreover, whatever the electrode shape, intensified charge-coupled device visualizations showed that many streamers initiate from the pulsed high-voltage electrode edge and propagate on the dielectric surface toward the DC voltage electrode at a mean velocity of about 1 mm ns−1. However, the streamer trajectory depends strongly on the electrode shape. Visualizations of the pressure waves induced by the different plasma actuators have been realized with a shadowgraph system. In the presence of a sliding discharge, every streamer is at the origin of three different pressure waves. The first hemispherical pressure wave results from streamer ignition at the edge of the pulsed high-voltage electrode, the head of the streamer acting as a point heat source. The second hemispherical pressure wave is due to the corona-type discharge that ignites from the negative DC high-voltage electrode when the streamer head gets closer. Finally, the third wave is a semi-cylindrical wave as each streamer acts as a line source of heat. To conclude, pressure measurements highlighted that the peak value of the pressure is nearly constant along the spanwise direction of the wire electrode as it presents high fluctuations with the sawtooth electrode, the maximum pressure being measured above the tips, where streamers are localized.

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The study of flow separation control by a nanosecond pulse discharge actuator

Cited by 34 publications

References 31 publications

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

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

On the effect of operating condition on separated-flow control by nanosecond pulse discharge actuators

Streamer propagation and pressure waves produced by a nanosecond pulsed surface sliding discharge: effect of the high-voltage electrode shape

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