Transcript Comments on Modeling Challenges and Opportunities for DBD

Comments on Modeling Challenges and
Opportunities for DBD
Richard Miles
Princeton University
Developing a detailed model of the DBD process is
important to aid in establishing opportunities for significant
improvement of performance and determining limitations
• Opportunities for dramatic improvement
•Local non uniformities along the electrode
•Dynamics of the breakdown process
• Deleterious phenomena that might be mitigated
•Charge build up
•Viscous Drag
LOCAL NON UNIFORMITIES
ALONG THE ELECTRODE
Plasma actuator based on asymmetric
dielectric barrier discharge
•Pioneer work by J.R. Roth
•Very successful applications to low-speed flow control: T. Corke et al.
Pitot tube measurements of force
for positive and negative half cycles
(Leonov et al 2011)
Enloe et al (2008) found that 97% of the force came from the negative
cycle by using a dielectric barrier discharge to drive a pendulum
Electrode shaping
(Leonov et al 2011)
sharp tip
At random location
At the tip location
Pitot tube measurements of force for
positive and negative half cycles along
“smooth” and “tipped” edges of electrode
(Leonov et al 2011)
Pitot tube measurements of force for
positive and negative half cycles along
edge of “smooth” and tipped electrode
(Leonov et al 2011)
Improve performance by
Shaped Electrodes
DYNAMICS OF THE BREAKDOWN PROCESS:
Backward Breakdown
Dynamics of Positive streamer
formation and force generation
(Likhanskii 2010)
Forward breakdown
Dynamics of Positive streamer
formation and force generation
(Likhanskii 2010)
Backward breakdown
Dynamics of Positive streamer
formation and force generation
(Likhanskii 2010)
Passive phase - Bias pushing
Time Evolution of the Force
Momentum Transfer with
Bias Applied
Improve performance by an
embedded semiconducting
layer to suppress
backward breakdown
Charge Buildup
Surface charge build up with
sinusoidal self sustained DBD
15 sec run of a DBD actuator operating with a 3 KHz
sinusoidal, 10 kV peak-to-peak driving potential
Surface pote
0.5
0.0
Surface Charge Build up with 2kV DC bias
and 4kV pulses at 20 kHz
-0.5
-1.0
-1.5
0
5
10
15
20
25
Distance, mm
Positive pulses
Negative pulses
Positive bias
Zero bias
Negative bias
2.5
1.5
Surface potential, kV
2.0
Surface potential, kV
Positive bias
Zero bias
Negative bias
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-1.5
0
5
10
15
20
25
0
5
10
15
20
25
Distance, mm
Distance, mm
Figure 16. Surface potential distribution. Applied voltage profile – 2 kV DC bia
Negative pulses kHz PRR
2.0
kV
1.5
1.0
Positive bias
Zero bias
Negative bias
Improve performance by Suppression
of charge build up using thin
partially conducting electrode
Viscous Loss
Viscous loss along
boundary layer
Self similar scaling, one profile measurement predicts the rest
Viscous velocity and momentum
loss along boundary layer
Improve performance by
designing new wing
configurations that
incorporate DBD devices
Ultra low drag wing with backward facing steps. DBD
devices are placed at the edges to avoid viscous losses and
operated to maintain performance during climb and
maneuvering