1. Janusz Podliński, Artur Berendt, Jerzy Mizeraczyk Centre for Plasma and Laser Engineering The Szewalski Institute of Fluid-Flow Machinery Polish Academy of Sciences Gdańsk, Poland Multi ‑ DBD actuator with floating interelectrode for aerodynamic control

2. Outline 2  Dielectric Barier Discharge (DBD) plasma actuators Applications Design  Our investigations Electrode shape Electrode at floating potential Multi-DBD plasma actuator  Summary

3. Actuator ON DBD plasma actuators 3 Actuator OFF Flow visualisation in an aerodynamic channel with a DBD plasma actuator DBD plasma actuator for flow modification Flow

4. DBD plasma actuators 4 DBD plasma actuator placed on an aerodynamic element can influence on: Boundary layer transition Wing tip vortex Leading and trailing flow separation DBD plasma actuators can change parameters of the airfoils Lift force increase Drag force decrease Noise reduction

5. 5 DBD plasma actuators Cross-section of the „classic” DBD plasma actuator Top-side view of the „classic” DBD plasma actuator

6. 6 Experimental set-up for DBD discharge parameters and flow measurements by PIV Our investigations

7. 7 U p-p =24 kV; I p =500 mA; f =1,5 kHz Classic DBD plasma actuators Without electrode gap With electrode gap 20 mm U p-p = 48 kV; I p =20 mA; f =1,5 kHz

8. 8 Saw-like electrodes for DBD plasma actuators Example of saw-like electrode Smooth electrode DBD plasma actuators with smooth and saw-like electrodes Electrode gap 20 mm U p-p = 52 kV, f = 1.5 kHz The discharge for actuators with smooth and saw-like electrode Effect of saw-like electrode  DBD starts at lower voltage  More uniform discharge along electrodes Saw-like electrode

9. 9 Maximum flow generated by the actuators with smooth and saw-like electrodes (d – distance between electrodes in mm) Flow velocity field measured by PIV Saw-like electrodes for DBD plasma actuators Effect of saw-like electrode  Higher flow velocities generated by DBD DBD plasma actuators with smooth and saw-like electrodes

10. 10 Multi-discharge plasma actuators Schematic design Double DBD plasma actuator possible ‘Classic’ Multi-DBD for actuators Multi-DBD with floating interelectrodes for actuators

11. 11 Multi-DBD actuator with floating interelectrodes Discharge visualisation - top view Length of all electrodes: 80 mm High voltage electrode width: 10 mm HV to floating interelectrode distance: 0 mm Grounded (1) to HV electrode distance: 0 mm Floating interelectrode width: 4 mm Floating to grounded (2) electrode distance: 4 mm Grounded electrode width: 3 mm High voltage: U pp = 32 kV, f = 1.5 kHz

12. 12 Length of HV and grounded electrodes: 50 mm Length of floating interelectrodes: 45 mm High voltage electrodes width: 15 mm HV and FL interelectrodes in optimum position Floating interelectrodes width: 3 mm Floating to grounded electrode distance: 6 mm Grounded electrodes width: 3 mm Grounded to floating electrode distance: 13 mm Dielectric: glass plate – 2 mm thick High voltage: U pp = 32 kV, f = 1.5 kHz Airflow velocity m/s Time-averaged streamlines of an airflow induced by the multi-DBD actuator with saw-like floating interelectrodes Multi-DBD actuator with floating interelectrodes Time-averaged streamlines

13. 13 Experimental set-up for leading edge flow separation control Wind tunnel Test section: 0.6 m x 0.46 m – 1.5 m long, Velocity  100 m/s, Turbulence level  0.1 % NACA 0012 model: Chord 200 mm Span 595 mm Multi-DBD actuator with saw-like floating interelectrode

14. 14 Plasma OFF – separated airflowPlasma ON - airflow reattachment U 0 = 15 m/sChord: 200 mm Incidence = 11 o Re = 200 000 Multi-DBD plasma actuator with saw-like floating interelectrode for leading edge flow separation control Applied HV: U HV = 15 kV f HV = 1.5 kHz U 0 = 15 m/sChord: 200 mm Incidence = 11 o Re = 200 000 Leading edge flow separation control - results Time-averaged flow velocity fields measured by PIV method

15. Summary 15 The DBD with saw-like electrodes: Lower onset voltage, More uniform discharge along electrodes, Higher airflow velocities than the DBD with smooth electrodes. The multi-DBD actuator with floating interelectrodes: Plasma generation on a large area of the dielectric surface, Maximum airflow velocity over 10 m/s, Attractive for aerodynamic applications.