# Enhancement of the electromechanical performances of a single dielectric barrier discharge actuator

Jérôme Jolibois, Éric Moreau

► To cite this version:

Jérôme Jolibois, Éric Moreau. Enhancement of the electromechanical performances of a single dielectric barrier discharge actuator. IEEE Transactions on Dielectrics and Electrical Insulation, 2009, 16 (3), pp.758-767. 10.1109/TDEI.2009.5128516. hal-00459938

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# Enhancement of the Electromechanical Performances of a Single Dielectric Barrier Discharge Actuator

J. Jolibois and E. Moreau

Laboratoire d'Etudes Aérodynamiques (LEA)
University of Poitiers, ENSMA, CNRS
2 Bd Marie et Pierre Curie, Teleport 2, BP 30179
86962, Futuroscope Chasseneuil Cedex, France

## ABSTRACT

In this paper, a parametric study of a single dielectric barrier discharge (SDBD) plasma actuator has been performed in order to enhance its electromechanical performances. Three input parameters have been investigated: the dielectric thickness, the waveform of the applied high voltage and the voltage slew rate. The goal is to increase the velocity of the discharge-induced electric wind and/or to reduce the electrical power consumption of the discharge. First, electrical measurements with high voltages ranging from 5 to 30 kV have been conducted, with a frequency set here to 1 kHz. This consisted of current recordings and electrical power consumption computations. Secondly, the velocity of the produced electric wind has been measured with a Pitot tube probe. From these velocity profiles, the maximum velocity, the produced mass flow rate and the electromechanical efficiency of the discharge have been determined. It highlights that the way to enhance the electromechanical performances of such a surface discharge consists in using a thick dielectric (at least a few millimeters) and a sine high voltage (several tens of kV) at a moderate frequency value.

**Index Terms** — Dielectric Barrier Discharge, Electric wind, Electrohydrodynamics, Flow control, Plasma actuator.

## 1 INTRODUCTION

Several studies have shown that surface discharges in air at atmospheric pressure may be used as an electrohydrodynamic (EHD) actuator for airflow control in aeronautics ([1-7] for instance). Applications like drag reduction, lift enhancement, flow reattachment or detachment, jet mixing or vectoring, skin friction and instability control are particularly concerned. For about 10 years, the “Electrofluidodynamique” group of the LEA (University of Poitiers) have been working on this topic in full expansion. A review has been recently published by Moreau [1].

In our University, three kinds of discharges have mainly succeeded in modifying actively flow characteristics: corona discharges, dielectric barrier discharges and sliding discharges. In these three cases, the actuator generates a weakly ionized plasma sheet on the surface of the profile and works by creating an electric wind and by injecting kinetic energy inside the boundary layer of the airflow. This electric wind results from collisions and momentum transfer from ions that drift between electrodes due to electric field, and the neutral particles of surrounding air. Usually, the produced electric wind acts as a jet of a few meters per second, tangentially to the profile wall.

In order to improve the ability of these plasma devices, several studies have focused on the discharge without free airflow because one solution to increase the plasma actuator effects for airflow applications consists in enhancing the velocity of the electric wind and the electrohydrodynamic force produced by the surface discharge [8-18].

In this paper, the discharge-induced electric wind is experimentally studied as a function of several parameters for a single dielectric barrier discharge (SDBD) actuator in absence of free airflow. This actuator consists of two metallic electrodes asymmetrically flush mounted on both sides of a dielectric plate. The active electrode is supplied with an AC high voltage and the other one is grounded. The discharge induces an airflow of several m/s tangentially and very close to the insulating wall, with velocity up to 7 m/s [11].

More specifically, a parametric study of a SDBD plasma actuator is performed in order to enhance its electromechanical performances. Three input parameters are investigated: the dielectric thickness, the waveform of the applied high voltage and the voltage slew rate. The goal is to increase the velocity of the discharge-induced electric wind and to reduce the electrical power consumption of the discharge.

For each parameter, electrical current measurements and electrical power consumption computations are conducted.
Velocity profiles of the produced electric wind above the wall plate are measured. Then, the maximum velocity, the produced mass flow rate and the electromechanical efficiency of the discharge are determined.

# 2 EXPERIMENTAL SET UP

## 2.1 THE SDBD ACTUATOR

The discharge setup consists of two flat 50-µm-thick rectangular electrodes made of aluminium tape asymmetrically flush mounted on each side of a dielectric plate (Figure 1). The active electrode is connected to a power amplifier (Trek model 30/20A, ± 30 kV, 20 mA) delivering high voltages up to 30 kV amplitude with a frequency set here to 1 kHz. The maximum delivered current peaks can reach about 500 mA. The maximum slew rate of the amplifier is equal to 500 V/µs. The other electrode is grounded. The dielectric plate is made of Polymethyl Methacrylate (PMMA) with a relative permittivity $ε_r$= 3.3 at 1 kHz and a dielectric strength of 15 kV/mm. Each electrode is 150 mm-long (spanwise) and 20 mm-wide. The electrode gap corresponds to the dielectric thickness (see Figure 1) but in fact, one considers that there is no air gap. This electrode configuration corresponds to the optimum geometrical case obtained by Forte et al. [11] in order to maximize the electric wind velocity.

When the SDBD is switched on, a plasma appears on both sides of the dielectric plate. It is directed from the emitting electrode towards the opposite electrode (see Figure 1). The discharge appears to be quasi-uniform. In fact, it is constituted of microdischarges distributed uniformly in time and space along the electrode length. Moreover, the discharge produces an electric wind by a momentum transfer between ions and ambient air. The velocity of the induced electric wind by discharge is between a few m/s up to 7 m/s [11].

<figure><img src="image_2.png" /><figcaption>Figure 1. Schematic side view of the SDBD.</figcaption></figure>

## 2.2 ELECTRICAL MEASUREMENTS

The applied voltage is measured by using the power amplifier internal probe. The current is deduced from the voltage across a non-inductive resistor (100Ω) connected in series between the grounded electrode and the earth. Both waveforms are recorded using a fast Lecroy digital oscilloscope model Wavesurfer 424 (200 MHz, 2 GS/s). A typical example of the voltage and current waveforms is given in Figure 2, for a 3 mm-thick actuator made of PMMA, a frequency of 1 kHz and a voltage amplitude of 16 kV. We can see that series of short and intense current pulses occur during

the first part of each half-period (or during the negative and positive-going cycles). Each pulse corresponds to one or several simultaneous microdischarges, appearing as soon as the voltage across the inter-electrode space exceeds a given threshold value. This current waveform results from both discharges, above and below the dielectric plate. If the grounded electrode is encapsulated, avoiding the discharge below the plate, then the resulting current is different [1].

From both voltage and current curves, the total electrical power consumption can be computed with:

$$P = \frac{1}{T} \int_{t=0}^{T} v(t) \times i(t) dt$$

with $v(t)$, $i(t)$ the measured voltage and current versus time, respectively, and $T$ is the waveform period. In practise, the time-averaged value computed with only one cycle would not allow to reach a convergent value because it should varies from one to another cycle. Then 20 cycles have been recorded, with a time resolution equal to 2 ns to be sure that the current peaks (typical duration of 10-20 ns) are well visualized.

<figure><img src="image_3.png" /><figcaption>Figure 2. Typical discharge current and voltage waveforms versus time.</figcaption></figure>

## 2.3 ELECTRIC WIND VELOCITY MEASUREMENTS

Measurements of the induced velocity above the actuator are realized with a total pressure probe made in glass connected to a Furness micromanometer FC014 (0–10 mm H₂O, 0–12 m/s). The probe can be moved precisely along 2 axes above the actuator with two Isel linear driving units monitored by a computer, one parallel to the wall (x axis, horizontal), the other one perpendicular to the surface (y axis, vertical). Coordinate (0,0) corresponds to the right edge of the HV electrode (see Figure 1). This setup allows to measure the time-averaged velocity component along the x axis. Vertical profiles are taken at different x values at the high voltage electrode side. The analogic output of the manometer is connected to a Keithley USB data acquisition module (16 bits, 50 kS/s). For each measurement, a record of 3,000 samples at 1 kHz is made to ensure the convergence of the time-averaged velocity value.

Typical velocity profiles above a SDBD actuator are shown in Figure 3 for different applied voltage values. As previously reported, we can see that the maximum velocity is measured at
about 0.3-0.5 mm above the wall and that it increases with the applied voltage [1, 10, 11].

From these velocity profiles, the mass flow rate Q produced by the discharge can be computed by:

$$Q = \rho \int_{y=0}^{\infty} u(y) dy$$

where ρ is the air density and u(y) the measured velocity above the dielectric plate, from the wall to the maximum value of y for which a velocity can be detected.

Moreover, the produced mechanical power P<sub>mech</sub> is computed from:

$$P_{\text{mech}} = \frac{1}{2} \rho L \int_{y=0}^{\infty} u^3(y) dy$$

with L the electrode length in spanwise (150 mm here). Then one can deduce the electromechanical efficiency by:

$$\eta = \frac{P_{\text{mech}}}{P}$$

with P<sub>mech</sub> the produced mechanical power and P the electrical power consumption.

<figure><img src="image_4.png" /><figcaption>Figure 3. Typical velocity profiles above the DBD actuator for several voltages.</figcaption></figure>

## 3 DIELECTRIC LAYER THICKNESS

In this section, the influence of the dielectric layer thickness on the electromechanical behavior of the discharge has been analyzed. All the discharge setups have the same configuration (20 mm-wide electrode, no air electrode gap and flat plate made of PMMA). Only the thickness varies. The thickness a of the barrier ranges from 0.5 mm to 5 mm (Figure 4). The waveform applied is a sine one, at a frequency set to 1 kHz.

For every thickness, the position in the x direction where the maximum velocity occurs has been determined. At this location, the profile of the discharge-induced velocity along y has been recorded, as well as the current and the electrical power.

First, we study the variation of the electrical power consumption as a function of the applied voltage amplitude for every insulating layer thickness. Figure 5 shows the electrical power consumption per unit length in spanwise (in W/cm) versus the applied voltage. It illustrates that it increases as

$$P = k(V - V_0)^2$$ where k is a coefficient depending on the geometrical configuration and the high voltage frequency [1, 10]. However the expression used by Roth & Daï [15] and Enloe et al. [13] ($P \propto V^n$ with $2 \le n \le 3$) fits correctly our experimental measurements. From Figure 5, we can see that at a given voltage, the electrical power consumption increases when the thickness of the insulating barrier decreases. This is due to the fact that the plasma generated with a thin dielectric presents a higher discharge current. The discharge established on a thin dielectric wall is more filamentary than the one produced on a thick barrier, resulting in high current peaks, and then in an electrical power increase.

<figure><img src="image_5.png" /><figcaption>Figure 4. Sketch of the experimental setup.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Figure 5. Evolution of the electrical power versus voltage for every thickness.</figcaption></figure>

It is assumed that the discharge extension along x increases with the applied voltage [11, 13] and the position at which the maximum electric wind velocity occurs, corresponds usually to the discharge extension limit [11]. To confirm this assumption, the position $X_{Umax}$ at which the maximum electric wind velocity occurs has been accurately determined. Figure 6 shows that this position increases linearly with the applied voltage amplitude, whatever the dielectric thickness.

Figure 7 presents the position of the maximum electric wind velocity as a function of the electrical power consumption. This plot has an asymptotic behavior whatever the thickness. More, we can see that at a given electrical power, the position
of the maximum electric wind velocity increases with the insulating wall thickness, because the applied voltage amplitude is higher for the thicker **dielectrics** (see Figure 5).

<figure><img src="image_7.png" /><figcaption>**Figure 6.** Evolution of the position of the maximum electric wind velocity versus voltage for every thickness.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>**Figure 7.** Evolution of the position of the maximum wind velocity versus electrical power consumption for every thickness.</figcaption></figure>

Figure 8 displays the maximum electric wind velocity versus the electrical power consumption, for 6 values of dielectric thickness. This plot has an asymptotic behavior whatever the thickness. Moreover, all the curves are nearly surimposed, meaning that all the actuators generate the same velocity, **whatever the dielectric thickness**.

This result is of great interest. On one hand, it demonstrates that the maximum electric wind velocity depends only on the electrical power consumption. On the other hand, the thickest dielectric actuator induces a more stable discharge when with the thinnest one, the discharge becomes more easily filamentary and unstable. In this mode, the plasma is concentrated on several injection points with energetic filaments which may damage the material due to a strong local heating. Then the dielectric may be broken down due a spark occurring between both electrodes across it. As a conclusion,

it is then better to use a thick dielectric layer to obtain a more robust actuator.

Furthermore, the asymptotic behavior of the curve highlights a significant tendency: beyond an electrical power consumption threshold equal to about 2 W/cm, the injected power does not contribute to produce velocity because a physical limit is certainly reached.

<figure><img src="image_9.png" /><figcaption>**Figure 8.** Maximum electric wind velocity versus electrical power consumption for every thickness.</figcaption></figure>

Figure 9 presents the velocity profiles above the SDBD actuator at a given electrical power of 1.4 W/cm for two thickness values. On one hand, it shows that the maximum velocity is quite similar in both cases. On the other hand, the area of the velocity profiles is wider when the dielectric is thicker. This may be due to the fact that the surface discharge established at the wall of the 0.5 mm thick layer is closer to the wall than the one produced at the wall of the thicker plate.

<figure><img src="image_10.png" /><figcaption>**Figure 9.** Velocity profiles above the SDBD actuator at a given electrical power for two actuators with different thickness.</figcaption></figure>

Figure 10 shows the mass flow rate versus electrical power consumption. It highlights that it increases with the dielectric thickness, because the velocity profile is thicker when the
electric wind is produced on a thicker dielectric wall (Figure 9).

Finally, the electromechanical efficiency, presented in Figure 11, is rather low (in the order of a few 0.01%) and it increases with the dielectric thickness. Note that this efficiency may be increased in encapsulating the ground electrode. Indeed, in such conditions, the current and then the electrical power consumption are divided by about two [12].

<figure><img src="image_11.png" /><figcaption>**Figure 10.** Mass flow rate versus electrical power consumption for every thickness.</figcaption></figure>

<figure><img src="image_12.png" /><figcaption>**Figure 11.** Efficiency versus electrical power for every thickness.</figcaption></figure>

discharge current for 3 waveforms (sine, triangle, and square ones) at 16 kV. The current curves presented here have been corrected in order to remove the background noise with the help of a software developed by Laurentie et al. [19]. At 16 kV and 1 kHz, the electrical power consumption is nearly the same for the sine and triangle waveforms (P ≈ 0.5 W/cm) when for the square one, the electrical power is equal to about 0.75 W/cm because high current peaks (up to 150 mA) occur during the positive rise.

<figure><img src="image_13.png" /><figcaption>**Figure 12.** Electrical power consumption versus voltage for several waveforms.</figcaption></figure>

<figure><img src="image_14.png" /><figcaption>**Figure 13.** Discharge current and voltage waveforms (sine) versus time.</figcaption></figure>

# 4 APPLIED WAVEFORMS

In this section we focus on the ability of the applied waveforms to modify the characteristics of the SDBD. In this experiment, the thickness is fixed at 3 mm.

First, we present the variation of the electrical power consumption as a function of the applied voltage amplitude (still at 1 kHz), for the different high voltage waveforms (Figure 12). We can observe that the electrical power consumption increases when the waveform presents high negative and positive-going cycles, ie. fast rise and fall times, because this results in high current peaks.

Figures 13, 14, and 15 display the temporal evolution of the
<figure><img src="image_15.png" /><figcaption>**Figure 14.** Discharge current and voltage waveforms (triangle) versus time.</figcaption></figure>

<figure><img src="image_16.png" /><figcaption>**Figure 15.** Discharge current and voltage waveforms (square) versus time.</figcaption></figure>

The evolution of the position of the maximum electric wind velocity $X_{Umax}$ as a function of the applied voltage amplitude is shown in Figure 16: it increases linearly with the applied voltage whatever the waveform, excepted the square one. For the square waveform, its seems that the position of the maximum electric wind velocity evolves according to a quadratic function. This difference of behavior may be due to the fact that the square waveform favors high current peaks. In this case, the extension of the discharge above the insulating wall is longer [20].

If we compare the evolution of the position of the maximum electric wind velocity versus the electrical power consumption, one can see that $x_{Umax}$ are nearly surimposed for all the waveforms, excepted for the square one (Figure 17).

<figure><img src="image_17.png" /><figcaption>**Figure 16.** Evolution of the position of the maximum electric wind velocity versus voltage for several waveforms.</figcaption></figure>

Figure 18 displays the maximum velocity versus the electrical power consumption. One more time, the velocity presents an asymptotic behavior. The discharge induces the same velocity whatever the waveform, excepted with the square and the positive sawtooth ones.

On one hand, this is a very interesting result because it shows, one more time, that the main input parameter which control the electric wind production in surface DBD is the electrical power consumption. On the other hand, the square and the positive sawtooth waveform high voltages result in a smaller electric wind velocity. In fact, time-resolved velocity measurements [11] proved recently that the negative-going cycle (or the negative half cycle) which produces a negative corona-like discharge results in a faster velocity than the positive-going one (or positive half cycle). When one uses a positive sawtooth waveform voltage, the positive corona-like discharge is favoured in spite of the negative one, resulting in a slower time-averaged electric wind velocity.

Concerning the square waveform HV, it seems that the presence of high current peaks occurring at each positive and negative-going cycle (with a slope equal here to 500 V/µs due to the maximum slew rate of the Trek amplifier) results in a electrical power increase whereas these peaks do not contribute efficiently to electric wind production compared to the ion drift because their duration is very short (≈ 10 ns) [21].
<figure><img src="image_18.png" /><figcaption>**Figure 17.** Evolution of the position of the maximum electric wind velocity versus electrical power consumption for several waveforms.</figcaption></figure>

<figure><img src="image_19.png" /><figcaption>**Figure 18.** Maximum electric wind velocity versus electrical power for several waveforms.</figcaption></figure>

As an example, Figure 19 presents velocity profiles above the SDBD actuator at a given electrical power of 0.75 W/cm for both waveforms, sine and square ones. It shows that at a similar power consumption, the sine voltage induces a faster electric wind with a discharge closer to the wall than the square waveform. This may be explained by the fact that a voltage of 18 kV is needed to consume 0.75 W/cm with the sine HV whereas only 16 kV are necessary in the case of the square HV. This confirms the fact that the lower effectiveness of the square voltage is due to losses during the negative and positive cycles, corresponding to high slope rise.

<figure><img src="image_20.png" /><figcaption>**Figure 19.** Velocity profiles above the SDBD actuator at a given electrical power for two waveforms.</figcaption></figure>

Figure 20 shows the mass flow rate produced by the SDBD versus electrical power consumption, for every waveform. It highlights that the mass flow rate increases with the electrical power, and that its values are quite similar whatever the waveform, excepted in the case of both sawtooth waveforms. In the case of the positive sawtooth waveform, it is due to the fact that the positive corona-like discharge is favoured in spite of the negative one, resulting in a decrease of the produced velocity [22]. In the case of the negative sawtooth, the mass flow rate is decreased because the velocity profiles is thinner.

For the same reason, the electromechanical efficiency of the SDBD when a negative sawtooth waveform is used is smaller (see Figure 21). However it is still increasing up to 1.6 W/cm with this waveform whereas it begins to decrease when the electrical power reaches about 1.1 W/cm for all the others waveforms (excepted for the square waveform). The efficiency decrease is due to the saturation of the produced mechanical power $P_{mech}$ for all waveforms excepted the negative sawtooth and the square. Beyond 1.1 W/cm, the discharge current is composed of high peaks. For example at 16 kV, the average peak current is equal to about 25 mA against 50 mA at 24 kV. These peaks do not contribute efficiently to electric wind production compared to the ion drift because their duration is very short [21].
<figure><img src="image_21.png" /><figcaption>**Figure 20.** Mass flow rate versus electrical power consumption for several waveforms.</figcaption></figure>

<figure><img src="image_22.png" /><figcaption>**Figure 21.** Evolution of the efficiency versus electrical power for several waveforms.</figcaption></figure>

# 5 INFLUENCE OF THE SLEW RATE

In order to confirm our previous results and assumptions, we study here the influence of the waveform slew rate on the performances of the SDBD. For this experiment, the geometrical configuration of the plasma actuator is the same as in the section 4 (20 mm-wide electrodes, no gap, 3 mm-thick PMMA plate).

In order to highlight the role of the slew rate, we apply to the discharge a high voltage of known slew rate and which can be modified. The voltage with the smallest slew rate is a triangle. By increasing its slew rate, this one becomes a trapezium and finishes by a square. There are three trapezium, called tra_1, tra_2 and tra_3, with a slew rate multiple (1, 2 and 4) of the origin slope of the sine waveform, ie. $dV/dt$ at $t=0$.

Figure 22 presents the electrical power consumption as a function of the applied voltage amplitude. It shows that the electrical power consumption increases with the slew rate of

the applied voltage. This is due to high current peaks that occur when the slew rate is increased.

As the high voltage amplifier delivers voltage with a maximum slew rate of 500V/µs, the slew rate of tra_3 is the same as the square one when the applied voltage is 18 kV. That is the reason why there is no measurement after 16 kV for the waveform called tra_3.

<figure><img src="image_23.png" /><figcaption>**Figure 22.** Evolution of the electrical power versus voltage for different slew rate.</figcaption></figure>

Figures 23, 24 and 25 show respectively the maximum velocity, the mass flow rate and the efficiency versus electrical power consumption. On one hand, as expected, the maximum velocity and the electromechanical efficiency at a given power decrease when the HV slew rate is increased.

On the other hand, the waveform of the applied HV has no effect on the produced mass flow rate. The explanation is given in Figure 26: when the slew rate is increased, the produced velocity is smaller close to the wall (for $y \le 1$ mm), but this velocity loss is compensated by a velocity gain for $y \ge 1.5$ mm. This point exhibits clearly that the slew rate of the applied HV affects significantly the plasma topology, and then the electric wind characteristics.

A similar result has been obtained by Boeuf et al. [23] on the space distribution of the time-averaged force parallel to the dielectric surface for three different values of the voltage slope.
<figure><img src="image_24.png" /><figcaption>**Figure 23.** Maximum electric wind velocity versus electrical power consumption for several slew rates.</figcaption></figure>

<figure><img src="image_25.png" /><figcaption>**Figure 24.** Evolution of the mass flow rate versus electrical power for different slew rates.</figcaption></figure>

<figure><img src="image_26.png" /><figcaption>**Figure 25.** Evolution of the efficiency versus electrical power for different slew rates.</figcaption></figure>

<figure><img src="image_27.png" /><figcaption>**Figure 26.** Velocity profiles above the SDBD actuator at a given electrical power with different slew rates.</figcaption></figure>

Moreover, a recent numerical work conducted by Lagmich et al. [24] shows that the parallel force above the SDBD increases when the slope of the ramp voltage (positive or negative) increases, contrary to our results. However, comparisons between those results and ours are difficult because we performed time-averaged velocity measurements by a total pressure probe and not force measurements. Moreover, the parameters which affect the induced electric wind velocity (electrode geometry, dielectric thickness, permittivity, voltage and frequency) are not the same in both studies. This could explain the differences between both experimental and computational studies.

# 7 CONCLUSION

A parametric study of a single dielectric barrier discharge plasma actuator has been performed in order to enhance its electromechanical performances. Three input parameters have been investigated: the dielectric thickness, the waveform of the applied high voltage and the voltage slew rate.

The main results are following:

(1) It is better to use a thick dielectric material (a few mm) instead of a thin one. Indeed, the reduction of the insulating layer thickness does not enable to produce a faster electric wind at a given electrical power. Moreover, the decreasing of the thickness modifies the discharge current and favours the dielectric breakdown.

(2) Whatever the dielectric thickness is (in a range from 0.5 to 5 mm), the maximum electric wind velocity depends only on the electrical power consumption. Indeed, at a given electrical power value, the produced velocity is similar for all the dielectric thicknesses. More, it seems that no more velocity is produced beyond the electrical power consumption threshold of about 2 W/cm.

(3) The electromechanical efficiency of the SDBD increases with the dielectric thickness. This may be explained by two competing effects. On one hand, with a thin dielectric, the
discharge current is higher but the applied voltage is smaller, resulting in a higher transferred charge and probably to a higher ionization rate, but in a smaller electric field. On the other hand, with a thick dielectric, the transferred charge is smaller but the electric field inside the discharge region is higher. This shows that one must increase the electric field to increase the electric wind velocity, instead of increasing the transferred charge by using a higher frequency for instance. This should be possible with high-quality dielectric materials.

(4) The produced electric wind depends significantly on the voltage waveform. When the waveform presents negative or positive-going cycles with steep slopes (it is the case of the square waveform for instance), this results in high current peaks which do not contribute efficiently to electric wind production.

To conclude, the best manner to produce the fastest electric wind at a given electrical power consumption consists of using a thick dielectric (a few mm), a high voltage with no high negative and positive-going slopes, at a moderate frequency (about 1 kHz).

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[20] V.I. Gibalov and G.J. Pietsch, "The development of dielectric barrier discharges in gas gaps and on surfaces", J. Phys. D: Appl. Phys., Vol. 33, No 20, pp. 2618-2636.

[21] J.P. Boeuf, Y. Lagmich, Th. Callegari, L.C. Pitchford and Th. Unfer, "New insights in the physics of the SDBD plasma actuators for flow control", Proc. of the 46th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, AIAA Paper 2008-1376, 2008.

[22] N. Balcon, N. Benard, Y. Lagmich, J.P. Boeuf, G. Touchard and E. Moreau, "Positive and negative sawtooth signals applied to a DBD plasma actuator - Influence on the electric wind", IEEE Dielectrics and Electrical Insulation Society, accepted.

[23] J.P. Boeuf, Y. Lagmich, Th. Unfer, Th. Callegari and L.C. Pitchford, "Electrodynamic force in dielectric barrier discharge plasma actuators", J. Phys. D: Appl. Phys., Vol. 40, No3, pp. 652-662.

[24] Y. Lagmich, Th. Callegari, L.C. Pitchford and J.P. Boeuf, "Model description of surface dielectric barrier discharges for flow control", J. Phys. D: Appl. Phys., Vol. 41, No 9, 095205.

Jérôme Jolibois was born in Amiens, France in 1980. He received the M.Sc. degree from the University of Poitiers, Poitiers, France in 2005. Actually, he is pursuing the Ph.D. degree in electrical engineering at the University of the Poitiers, Poitiers, France.

His research interests include the physics and application for airflow control of the surface discharges.

Eric MOREAU was born in France on February 1, 1969. He received the Ph.D. degree in Electrical Engineering in 1997 from the University of Poitiers, France, and he became Assistant Professor in 1998.

He is presently Professor in Electrical Engineering at University of Poitiers, and he is at the head of the "électrofluidodynamique" research group at "Laboratoire d'Etudes Aérodynamiques", CNRS.

His area of interest is Electrohydrodynamic. He has been working on different topics such as flow electrification, electrokinetic phenomena in porous media and soil decontamination. Since 1999, he has been in charge of a new research topic concerning plasma actuators for airflow control. His works consist firstly in studying the electric wind produced by surface discharges in air at atmospheric pressure, and secondly in investigating their effects on aerodynamic airflows. For a few years, he has been working in electrostatic precipitation and plasma for depollution applications.

He is author or coauthor of about 50 articles published in international journals, and more than 80 papers in proceedings.