1. Flow Control over Trapezoidal-Wing Planforms with Sharp Edges
José M. Rullán, Pavlos Vlachos and Demetri Telionis
Dept. of Engineering Science and Mechanics

2. Overview Background Facilities and models Experimental setup Results
Conclusions
Acknowledgement

3. Background
Trapezoidal wings common in today’s fighter aircrafts as well as unmanned controlled aircrafts.
Little understanding of aerodynamic effects at sweeping angles between 30° and 40° AOA.
Biconvex is reason for trying work on a circular arc airfoil.

4. Background (cont.)
Exhibit behavior of unswept wings and/or delta wings
Shear layer is a vorticity layer

5. Yaniktepe and Rockwell
Sweep angle 38.7º for triangular planform
Flow appears to be dominated by delta wing vortices
Interrogation only at planes normal to flow
Low Re number~10000
Control by small oscillations of entire wing
Flaps not a choice for stealth.

6. Earlier Wind Tunnel Tests
Pressure measurements
Stability Wind Tunnel with U∞=40 m/s Re≈1,200,000
44” span trapezoidal wing

7. Facilities and models Water Tunnel with U∞=0.25 m/s Re≈30000
CCD camera synchronized with Nd:YAG pulsing laser
13 angle of attack
Actuating at shedding frequency of 1.71 Hz
8” span trapezoidal wing
Flow control supplied at inboard half of wing
Disturbance closest to separation point to try to disturb at different AOA. Cmu ratio of momentum introduced to flow momentum seen by airfoil.
Shedding frequency is obtained from the projected frontal width instead of the chord.

8. Wind Tunnel Model
Model is hollow. Leading edge slot for pulsing jet

9. Facilities and models(cont.)
planes
z/c
z/b 1
0.068
0.092 2
0.156
0.209 3
0.249
0.334 4
0.340
0.456 5
0.417
0.559 6
0.467
0.626 7
0.531
0.711 8
0.581
0.778 9
0.644
0.863 10
0.694
0.930
x/c A
0.28 B
0.513 C
0.746 D
1.086
Disturbance closest to separation point to try to disturb at different AOA. Cmu ratio of momentum introduced to flow momentum seen by airfoil.
Shedding frequency is obtained from the projected frontal width instead of the chord.

10. Coordinate system
Profiles taken at location of midpoint

11. Trefftz Plane (Re=1,200,000, =13°)
Axial velocity Vorticity

12. Actuation
Time instants of pulsed jet
(a)
(b)
(c)

13. Results
Velocity vectors and vorticity contours along a plane D, no control (left) and control (right).
Actuator increases back pressure, no secondary frequencies introduced so it does not suffer from nonlinear interactions

14. Vortex Patterns
Visbal and Gursul call it “dual vortex structure”

15. PIV results (cont.)
Planes 2(z/b= 0.209) and 3 (z/b= 0.334) with actuation.
Steady profiles are not smooth and tend to even out after z/H=4.
Deviation from centerline is more pronounced for pulsating and jet is also more compact.

16. Results (cont.)
Plane A, control, t=0,t=T/8

17. Results (cont.)
Plane A, control, t=2T/8,t=3T/8

18. Results (cont.)
Plane A, control, t=4T/8,t=5T/8

19. Results (cont.)
Plane A, control, t=6T/8,t=7T/8

20. Results (cont.)
Plane 8, t=0
No control Control

21. Results (cont.)
Plane 8, t=T/8
No control Control

22. Results (cont.)
Plane 8, t=2T/8
No control Control

23. Results (cont.)
Plane 8, t=3T/8
No control Control

24. Results (cont.)
Plane 8, t=4T/8
No control Control

25. Results (cont.)
Plane 8, t=5T/8
No control Control

26. Results (cont.)
Plane 8, t=6T/8
No control Control

27. Results (cont.)
Plane 8, t=7T/8
No control Control

28. Results (cont.)
Planes B and C, control

29. Results (cont.)
Plane 10, t=0
No control Control

30. Results (cont.)
Plane 10, t=T/8
No control Control

31. Results (cont.)
Plane 10, t=2T/8
No control Control

32. Results (cont.)
Plane 10, t=3T/8
No control Control

33. Results (cont.)
Plane 10, t=4T/8
No control Control

34. Results (cont.)
Plane 10, t=5T/8
No control Control

35. Results (cont.)
Plane 10, t=6T/8
No control Control

36. Results (cont.)
Plane 10, t=7T/8
No control Control

37. Results (cont.)
Plane D, no control and control

38. Conclusions WITH ACTUATION:
Vorticity normal to stream is larger in magnitude than axial vorticity
Axial vorticity is also enhanced
Dual vortical patterns are activated and periodically emerge downstream
Flow is better organized

39. Future Work Obtain shedding frequency as function of span
Optimization of perturbation

40. Questions?