opportunities for dramatic improvement local non uniformities along the electrode dynamics of the...
TRANSCRIPT
• 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
Comments on Modeling Challenges and Opportunities for
DBDRichard Miles
Princeton UniversityDeveloping a detailed model of the DBD process is important to aid in establishing opportunities for significant improvement of performance and determining limitations
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 Charge Build up with 2kV DC bias and 4kV pulses at 20 kHz
0 5 10 15 20 25-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
Sur
face
pot
entia
l, kV
Distance, mm
Positive biasZero biasNegative bias
Positive pulses
0 5 10 15 20 25
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Negative pulses
Su
rfa
ce p
ote
ntia
l, kV
Distance, mm
Positive bias Zero bias Negative bias
0 5 10 15 20 25-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
Sur
face
pot
entia
l, kV
Distance, mm
Positive biasZero biasNegative bias
Positive pulses
0 5 10 15 20 25
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Negative pulses
Su
rfa
ce p
ote
ntia
l, kV
Distance, mm
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