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Flow Control over Sharp-Edged Wings Study

Research on flow control over sharp-edged wings with aerodynamics at high angles, separated flow control findings, and experimental tools used. Results, facilities, models, and conclusions highlighted.

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Flow Control over Sharp-Edged Wings Study

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  1. Flow Control over Sharp-Edged Wings José M. Rullán, Jason Gibbs, Pavlos Vlachos, Demetri Telionis Dept. of Engineering Science and Mechanics

  2. Flow Control Team P. Vlachos J. Rullan J. Gibbs

  3. Overview • Background • Facilities and models Experimental tools (PIV, pressure scanners, 7-hole probes) • Results: • Aerodynamics of swept wings • Flow Control at high alpha • CONTROL SEPARATED FLOW (NOT SEPARATION) • 10 4 < Re < 10 6 • Conclusions

  4. Background • Diamond-Planform, sharp-edged wings common on today’s fighter aircraft. • Little understanding of aerodynamic effects at sweeping angles between 30° and 40° AOA.

  5. Vorticity Rolling over Swept Leading Edges Sweep> 500 Sweep~450 Sweep~400 Sweep~400

  6. Background (cont.) • Low-sweep wings stall like *unswept wings or *delta wings Dual vortex structures observed over a wing swept by 50 degrees at Re=2.6X104 (From Gordnier and Visbal 2005)

  7. Yaniktepe and Rockwell • Sweep angle 38.7ºfor 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

  8. Facilities and models • VA Tech Stability Wind Tunnel • U∞=40-60 m/s Re≈1,200,000 • 44” span diamond-planform wing

  9. Facilities and models • Water Tunnel with U∞=0.25 m/s Re≈30000 • CCD camera synchronized with Nd:YAG pulsing laser • Actuating at shedding frequency

  10. Wind Tunnel Model • Model is hollow. • Leading edge slot for pulsing jet • 8” span diamond wing • Flow control supplied at inboard half of wing

  11. Facilities and models(cont.)

  12. Time-Resolved DPIV Sneak Preview of Our DPIV System • Data acquisition with enhanced time and space resolution ( > 1000 fps) • Image Pre-Processing and Enhancement to Increase signal quality • Velocity Evaluation Methodology with accuracy better than 0.05 pixels and space resolution in the order of 4 pixels

  13. DPIV Digital Particle Image Velocimetry System III Conventional Stereo-DPIV system with: • 30 Hz repetition rate (< 30 Hz) 50 mJ/pulse dual-head laser • 2 1Kx1K pixel cameras Time-Resolved Digital Particle Image Velocimetry System I • An ACL 45 copper-vapor laser with 55W and 3-30KHz pulsing rate and output power from 5-10mJ/pulse • Two Phantom-IV digital cameras that deliver up to 30,000 fps with adjustable resolution while with the maximum resolution of 512x512 the sampling rate is 1000 frme/sec Time-Resolved Digital Particle Image Velocimetry System II : • A 50W 0-30kHz 2-25mJ/pulse Nd:Yag • Three IDT v. 4.0 cameras with 1280x1024 pixels resolution and 1-10kHz sampling rate kHz frame-straddling (double-pulsing) with as little as 1 msec between pulses Under Development: • Time Resolved Stereo DPIV with Dual-head laser 0-30kHz 50mJ/pulse • 2 1600x1200 time resolved cameras • …with build-in 4th generation intensifiers

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

  15. PIV Results • Velocity vectors and vorticity contours along Plane D no control control

  16. PIV results (cont.) • Planes 2(z/b= 0.209) and 3 (z/b= 0.334) with actuation. Plane 2 Plane 3

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

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

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

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

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

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

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

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

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

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

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

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

  29. Results (cont.) • Plane 9, t=0 No control Control

  30. Results (cont.) • Plane 9, t=T/8 No control Control

  31. Results (cont.) • Plane 9, t=2T/8 No control Control

  32. Results (cont.) • Planes B and C, control

  33. Results (cont.) • Plane D, no control and control

  34. Flow animation for Treft planes

  35. Plane B Circulation variation over one cycle Plane A Plane B Plane A Plane C Plane D

  36. Plane D Circulation Variation (cont.) • Plane C

  37. Pressure ports location Spanwise blowing nozzles

  38. Full flap ESM Pressure profiles @ 13 AOA for Station 3 • Half flap

  39. Full flap ESM Pressure profiles @ 13 AOA for Station 4 • Half flap

  40. Full flap ESM Pressure profiles @ 13 AOA for Station 5 • Half flap

  41. Full flap ESM Pressure profiles @ 13 AOA for Station C • Half flap

  42. Stations 5-7 Stations 8-10 Pressure distributions for α=130.

  43. Stations 5-7 Stations 8-10 Pressure distributions for α=170.

  44. Conclusions WITH ACTUATION: • Dual vortical patterns are activated and periodically emerge downstream • Vortical patterns are managed over the wing • Suction increases with control • Oscillating mini-flaps and pulsed jets equally effective • Flow is better organized • Steady point spanwise blowing has potential

  45. Future Work • Study effect of sweep with new model • Explore the frequency domain • Identify local “3-D actuators” to control these 3-D flow fields • Aim at controlling forces and moments

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