1. Active flow control by plasma actuators for drag reduction Romain Futrzynski, Julie Vernet KTH School of Engineering Sciences

2. The plasma actuator, a.k.a. SDBD 2014-10- 08/09 KTH School of Engineering Sciences www.kth.se2 Two electrodes on a surface A high voltage ionizes the air in-between (plasma) Charged particles entrain the surrounding fluid A wall jet is created Single Dielectric Barrier Discharge:

3. Test-case geometry KTH School of Engineering Sciences www.kth.se3 Reduce drag Target A-pillars of the truck Rounded corner Dimensions? Flow angle? Cylinder Need for symmetry Half-submerged cylinder Single actuator Angle changes easily 2014-10- 08/09

4. KTH School of Engineering Sciences www.kth.se4 2014-10- 08/09 Test-case geometry

5. Numerical model KTH School of Engineering Sciences www.kth.se5 (x,y) SDBD 2014-10- 08/09

6. Model optimization KTH School of Engineering Sciences www.kth.se6 2014-10- 08/09

7. LES simulation, 11M cells Re D ~ 65 x 10 3 Crossflow case KTH School of Engineering Sciences www.kth.se7 2014-10- 08/09

8. Crossflow case: drag reduction KTH School of Engineering Sciences www.kth.se8 2014-10- 08/09

9. Setup of the separation control experiment -2 DBD plasma actuators -Active edge electrodes separated by 20 degrees KTH School of Engineering Sciences www.kth.se9 2014-10- 08/09

10. Setup of the separation control experiment -2 DBD plasma actuators -Active edge electrodes separated by 20 degrees KTH School of Engineering Sciences www.kth.se10 2014-10- 08/09

11. Setup of the separation control experiment -46 static pressure taps on the plate and cylinder Flow measurement techniques: -Static pressure taps on the plate and on the cylinder linked to a mechanical scanivalve U U KTH School of Engineering Sciences www.kth.se11 2014-10- 08/09 - - -

12. Setup of the separation control experiment -Boundary layer is tripped to have a turbulent boundary approaching the cylinder 0.5 mm Flow measurement techniques: -Hot wire measurements of the turbulent boundary layer developing upstream the cylinder (only baseline case) KTH School of Engineering Sciences www.kth.se12 2014-10- 08/09

13. Setup of the separation control experiment -Extremity of Pitot tube made of capillary glass tube Diameter ext.: 0.80 mm Diameter int.: 0.56 mm Flow measurement techniques: -Pitot and static probe measurements in the wake KTH School of Engineering Sciences www.kth.se13 2014-10- 08/09

14. θ = 95 deg. KTH School of Engineering Sciences www.kth.se14 2014-10- 08/09 - - - - - -

15. A body force model can reproduce the effect of an actuator Drag reduction is obtained both numerically and experimentally Significant drag reduction seems to require either -Higher actuator strength (simulations) -Two consecutive actuators (experiments) Work can be done to understand where the drag reduction comes from and how to maximize it Conclusions KTH School of Engineering Sciences www.kth.se15 2014-10- 08/09