Opportunities for dramatic improvement Local non uniformities along the electrode Dynamics of the breakdown process Deleterious phenomena that might be.

• 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