PIV test investigation on flow characteristics induced by plasma
aerodynamic actuation of different time scale
X. D. Wang1, H. Liang2, H. M. Song1, J. X. Bai2, X. F. Shi2, X. D. Shang2
( 1Plasma Dynamics Lab, Engineering College, Air Force Engineering University, Xi'an, 710038 China
2
Training Center, the Fifth Flight College of the Air Force, WuWei, 733003 China )
Abstract: Plasma flow control, as a novel active flow control technique, has become a newly-rising focus of
international aerodynamics and aerothermodynamics fields. PIV test investigations on flow characteristics
induced by plasma aerodynamic actuation were done in the paper. The results showed that the flow induced by
millisecond plasma aerodynamic actuation comes out as starting vortex and wall jet. The maximal velocity
induced by millisecond discharge is about 5 m/s. The higher the voltage is, the stronger the starting vortex and the
wall jet are. While the maximal velocity induced by nanosecond plasma aerodynamic actuation is about 0.5 m/s
and the flow is similar to a shock wave upward. The discharge current for nanosecond discharge is 4 A which is
much higher than that of millisecond discharge (0.1 A). So the nanosecond discharge results in a local fast heating
due to high reduced electric field. The local heating caused pressure and temperature rise. The propagation of the
pressure and heat induces shock wave and vortex which can enhance momentum and energy exchange between
the boundary layer and inflow greatly. So nanosecond discharge is more effective than millisecond discharge in
flow separation control. The results are instructional for increasing the ability of plasma flow control and can lay a
foundation for the understanding of nanosecond discharge plasma flow control.
Keywords: induced flow; PIV; plasma aerodynamic actuation; microsecond discharge; nanosecond discharge
1. Introduction
Plasma flow control, as a novel active flow
control technique, has become a newly-rising focus
of
international
aerodynamics
and
aerothermodynamics fields for its potential
application prospects in drag reduction and lift
augmentation of aircrafts and stability extension and
efficiency improving of aero engines. Plasma flow
control has several distinct advantages associated
with plasma actuators, including the absence of
complicated mechanical systems, their low weights
and sizes, their operation over a broad range of
frequencies, as well as their relative low power
consumption.
The characteristics tests of plasma aerodynamic
actuation are of vital importance in the mechanism
understanding for plasma flow control. A lot of
works devoted to characteristics diagnosis has
appeared in the past ten years[1-5]. Most of the
previous experimental and simulation studies mainly
focused on the asymmetric dielectric barrier
discharge plasma aerodynamic actuation excited by
sinusoidal or sawtooth voltage waveforms at
amplitude of 2-20 kV and frequency of 1-100 kHz,
which can be named as the microsecond discharge
plasma aerodynamic actuation. In paper6, the
acceleration effects of the microsecond discharge
were investigated. In paper7, the velocity profile was
measured by PIV tests. In the study8, the velocity of
the boundary layer was tested by pitot probe.
In order to better understand the underlying
physical mechanism of nanosecond discharge
plasma flow control, it is important to investigate the
unsteady characteristics of the nanosecond discharge
plasma aerodynamic actuation. In this paper, PIV
test investigation on flow induced by plasma
aerodynamic actuation of different time scale was
done.
2. Experimental Setup
A schematic of the dielectric barrier discharge
plasma aerodynamic actuator is shown in Fig. 1. The
dielectric layer used is a RO4350B (Rogers
Corporation) plate with a relative permittivity
constant of 3.48. The electrodes are made of copper,
covered with lead-tin film. The lower electrode,
which is covered with silica gel, is grounded. The
output voltage and the frequency range of the power
0.10
6
voltage(kV)
voltage
0.06
current
0.04
2
0.02
0.00
0
-0.02
-2
-0.04
current(A)
0.08
4
-0.06
-4
-0.08
-6
-0.00009
-0.00008
-0.00007
-0.00006
-0.00005
-0.10
-0.00004
t/s
Figure 2. Discharge voltage and current for microsecond discharge
12
4
10
voltage
8
3
current
2
6
4
1
2
0
0
-2
-1
current(A)
voltage(kV)
supply used for microsecond discharge are 0-40 kV
and 6-40 kHz, respectively. The output voltage and
the frequency range of the power supply used for
nanosecond discharge are 5-80 kV and 0.1-2 kHz,
respectively. The rise time and full width half
maximum (FWHM) are 10-30 ns and 30-50 ns,
respectively. The applied voltage and the discharge
current are measured by a high voltage probe
(Tektronix P6015A) and a current probe (Tektronix
TCP312+TCPA300). Signals are recorded on an
oscilloscope (Tektronix DPO4104). The velocity
and vorticity induced by the plasma aerodynamic
actuation are measured by Particle Image
Velocimetry (Lavision).
A high repetition double pulsed Nd:YAG laser
(135mJ/pulse) was used as the light source. The
interval of the laser pulse was 120ns. The repetition
rate of the each laser was 5 kHz. The resolution of
the camera was 1600pix ×1200pix. The air is seeded
by vaporization of mineral oil with a mean size of
about 0.3 µm. The flow characteristics of both the
nanosecond discharge and microsecond discharge
plasma aerodynamic actuation are measured.
-4
-2
-6
-8
-0.000002
-0.000001
0.000000
0.000001
-3
0.000002
t/s
Figure 2. Discharge voltage and current for nanosecond discharge
3.2 The flow induced by microsecond discharge
The cross-correlation function of the test area is
shown in figure 4. The peak value of the
cross-correlation function is obvious. It is verified
that the seed particle is traveling with the flow
velocity and the tests results are reliable.
Figure 1. A schematic of the asymmetric surface dielectric
barrier discharge plasma aerodynamic actuator(not to scale). d1 =
2 mm. d2 = 2 mm. Δd = 0 mm. hd = 0.5 mm. he = 0.035mm.
3. Experimental results and conclusions
3.1 Electrical Characteristics
The measurements of the applied voltage and the
discharge current are shown in Fig. 2 and 3.
We can see from figure 2 and 3 that the applied
voltage for microsecond discharge and nanosecond
discharge are nearly of the same value. But the
maximal discharge current for microsecond
discharge is 0.1 A, the nanosecond discharge is 4A
which is much bigger than that of millisecond
discharge and microsecond discharge. The bigger
the discharge current is, the stronger the instant
actuation intensity is.
Figure 4. The cross-correlation function near the actuator
The velocity and vorticity induced by millisecond
plasma aerodynamic actuation in stationary air are
shown in Fig. 4. The applied voltage was 12 kV. The
actuator was positioned at x=50 mm. The maximal
induced velocity is about 5 m/s, it appears 5 mm
downstream the actuator. In the early stage, a
vortex is bigger than that of the wall jet, that is to
say, the discharge intensity of beginning stage is
stronger than that of the steady stage.
80
80
60
60
60
40
20
y/mm
80
y/mm
y/mm
starting vortex is induced at t=1/3 s. The starting
vortex develops into a quasi-steady wall jet finally at
t=2.5 s. The velocity and vorticity of the starting
40
20
actuator
20
actuator
60
80
100
120
actuator
60
80
x/mm
100
120
60
(b) t=1/12s
60
60
y/mm
60
y/mm
80
40
20
20
80
100
100
120
40
20
actuator
actuator
120
(c) t=1/3s
80
40
100
x/mm
80
60
80
x/mm
(a) t=0
y/mm
40
actuator
60
120
80
100
120
60
80
x/mm
x/mm
x/mm
(d) t=1/2s
(e) t=1s
(f) t=2.5s
Figure 3. PIV test results of velocity and vorticity induced by millisecond plasma aerodynamic actuation
induced by nanosecond plasma aerodynamic
actuation is about 0.5 m/s, which is much less than
that of the millisecond plasma aerodynamic
actuation. Secondly, the flow induced by
nanosecond plasma aerodynamic actuation develops
slowly. It turns into steady wall jet at t=10s. Thirdly,
the flow induced by nanosecond plasma actuation is
not in the form of starting vortex and wall jet, it is be
similar to a shock wave upward.
3.3 The flow induced by nanosecond discharge
The flow induced by nanosecond plasma
aerodynamic actuation is shown in Fig. 7. The
applied voltage is 10kV and the pulse frequency is
f=1.8 kHz. The actuator is positioned at x=35mm.
We can see from the figure that it is different from
the flow induced by millisecond plasma
aerodynamic actuation. Firstly, the maximal velocity
40
20
60
y/mm
60
y/mm
y/mm
60
40
20
0
20
0
0
50
x/mm
(a) t=0
100
40
0
0
50
x/mm
(b) t=1/12 s
100
0
50
x/mm
(c) t=1/2 s
100
40
20
60
y/mm
60
y/mm
y/mm
60
40
20
0
20
0
0
50
100
0
0
x/mm
50
100
0
x/mm
(d) t=1 s
y/mm
y/mm
60
40
20
20
0
50
100
40
20
0
0
100
(f) t=3 s
60
40
50
x/mm
(e) t=2 s
60
y/mm
40
0
0
x/mm
50
100
x/mm
0
50
100
x/mm
(g) t=6 s
(h) t=8 s
(i) t=10 s
Figure 7. PIV test results of velocity and vorticity induced by nanosecond plasma aerodynamic actuation
In Fig.7 the induced flow direction by nanosecond
discharge is vertical to the dielectric layer surface,
while the flow induced by microsecond discharge
plasma aerodynamic actuation is parallel to the
dielectric layer surface. Due to the higher ionization
and dissociation degrees in the nanosecond
discharge plasma, the local particle density near the
electrode is also higher, which induces stronger local
pressure rise and then the vertical air flow.
4. Conclusions
To summarize, the flow induced by millisecond
plasma aerodynamic actuation comes out as starting
vortex and wall jet. The maximal velocity induced
by millisecond discharge is about 5 m/s. The higher
the voltage is, the stronger the starting vortex and the
wall jet are. While the maximal velocity induced by
nanosecond plasma aerodynamic actuation is about
0.5 m/s and the flow is similar to a shock wave
upward. The discharge current for nanosecond
discharge is 4 A which is much higher than that of
millisecond discharge (0.1 A). So the nanosecond
discharge results in a local fast heating due to high
reduced electric field. The local heating caused
pressure and temperature rise. The propagation of
the pressure and heat induces shock wave and vortex
which can enhance momentum and energy exchange
between the boundary layer and inflow greatly. So
nanosecond discharge is more effective than
millisecond discharge in flow separation control.
References
[1] Moreau E. Airflow control by non-thermal plasma
actuators[J]. Journal of Physics D: Applied Physics, 2007,
40(3): 605-636
[2] Corke T C, Enloe C L, Wilkinson S P. Dielectric
barrier discharge plasma actuators for flow control[J].
Annual Review of Fluid Mechanics, 2010, 42: 505-529
[3] Moreau E. Airflow control by non-thermal plasma
actuators[J]. Journal of Physics D: Applied Physics, 2007,
40: 605-636
[4] Santhanakrishnan A, Jacob J D. Flow control with
plasma synthetic jet actuators[J]. Journal of Physics D:
Applied Physics, 2007, 40: 637-651
[5] Porter C O, Baughn J W, McLaughlin T E, et al.
Plasma actuator force measurements[J]. AIAA Journal,
2007, 45(7): 1562-1570
[6] Boxx, I.G, Newcamp, J.M, et al. A piv study of a
plasma discharge flow-control actuator on a flat plate in an
aggressive pressure induced separation[R]. GT2006-91044
[7] Do H, Kim W, Mungal M G, et al. Bluff body flow
separation control using surface dielectric barrier
discharges[R]. AIAA 2007-0939
[8] Forte M, Moreau E, Touchard G., et al. Optimization
of a dielectric barrier discharge actuator[R]. AIAA
2006-2863