1. Order of Magnitude Improvement of SDBD Actuator Effect
T. Corke, F. Thomas, D. Orlov,
M. Iqbal, A. Kozlov,
H. Othman, D. Shatzman
Center for Flow Physics and Control
Aerospace and Mechanical Engineering
University of Notre Dame
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

2. Questions: How do we improve the performance of SDBD plasma actuators?
What are the governing properties?
What is the ultimate performance limit?
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

3. Approach: Develop space-time model for ionization in SDBD operation.
Include amplitude and frequency effects.
Not including maximum limits.
Compare to experiments.
Perform experiments that investigate limiting conditions on SDBD design and operation parameters.
Develop a theory to be included in space-time model.
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

4. SDBD Actuators: What we know
Three time scales:
Micro discharges (nsec)
a.c. period (.1ms)
Fluid response (10ms)
Ionization space-time dependent.
Static models give wrong results (e.g. fb~V2).
Temporal/space-uniform models give correct V-dependence (fb~V7/2), need spatial weighting
Space-time models give correct V, frequency and space dependence (Orlov, 2006).
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

5. Steps to model actuator in flow
Space-time electric potential, 
Space-time body force
Flow solver with body force added
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

6. Space-time model
Physical space over the encapsulated electrode is divided into N parallel networks.
Each parallel network consists of air capacitor, dielectric capacitor, plasma resistive elements and zenor diodes.
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

7. Model circuit elements
air capacitor
dielectric capacitor
Voltage on the dielectric surface in the n-th sub-circuit
Plasma current
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

8. Model Time Series Vn (t) Ipn (t) t/Ta.c. t/Ta.c. 5 1 5 1 Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

9. Model Space-time Characteristics
Experiment
Illumination
Model Ip(t)
dxp/dt
(xp)max
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

10. Plasma Propagation Characteristics
Effect of Vapp
dxp/dt vs Vapp
(xp)max vs Vapp
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

11. Plasma Propagation Characteristics
Effect of fa.c.
dxp/dt vs fa.c.
(xp)max vs fa.c.
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

12. Numerical solution for (x,y,t)
Model provides time-dependent B.C. for 
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

13. Body Force, fb(x,t) Y Normalized fb(x,t) t/Ta.c.=0.2 t/Ta.c.=0.7
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

14. Frequency Dependence of fb & Wp
Impact: Optimum frequency for body force.
Depends on actuator capacitance.
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

15. What limits maximum body force?
SDBD Plasma actuator is voltage driven,
fb~V7/2.
Not current driven like voice-coil type actuators.
For fixed power (I·V), one needs to limit current to maximize voltage.
What governs maximum achievable voltage for fixed power?
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

16. Maximum Voltage Optimization
Investigated different parameters on thrust produced by actuator
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

17. Order of Magnitude Improvement
Imax
Imax
Material 
Quartz 3.8
Kapton 3.4
Teflon 2.0
Imax
Imax
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

18. Premise
The maximum voltage at fixed power is limited by local electric field exceeding breakdown of air.
Thicker dielectrics and/or lower dielectric constants reduce capacitance of actuator and reduce concentration of electric field lines.
Other parameters?
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

19. Effect of frequency on Vmax
1kHz
0.25in. quartz glass
2kHz
Vmax(f)
4kHz
8kHz
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

20. Effect of dielectric thickness on Vmax
quartz glass; 1,2,4,8kHz
Tmax ~ Vmax
fa.c. ~ (t/)d
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

21. Tmax Efficiency 0.25in. quartz glass Nov. 8, 2006 AF Academy Workshop
on Plasma Actuators

22. Answers to Questions:
To improve the performance of SDBD plasma actuators?
Maximize V for fixed power.
Minimize I by preventing formation of strong plasma filaments.
Governing properties?
Dielectric design (t & ) and a.c. frequency.
Ultimate performance limit?
Maximum local E-field for air breakdown?
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators

23. Further Improvements: Additive Effect
Nov. 8, 2006
AF Academy Workshop
on Plasma Actuators