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Flow Control over Swept, Sharp-Edged Wings

Flow Control over Swept, Sharp-Edged Wings. Supported by US Air Force Office of Scientific Research. José Rullán, Jason Gibbs, Pavlos Vlachos, Demetri Telionis. Dept. of Engineering Science and Mechanics. Flow Control Team. P. Vlachos. J. Rullan. J. Gibbs. Overview. Background

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Flow Control over Swept, Sharp-Edged Wings

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  1. Flow Control over Swept, Sharp-Edged Wings Supported by US Air Force Office of Scientific Research José 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) • Actuators Mini-flaps, pulsed jets • Results: • Circular-arc airfoils • Swept wings • Flow Control at high alpha • 10 4 < Re < 10 6 • Conclusions

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

  5. Background (cont.) • Low-sweep wings stall like *unswept wings or *delta wings

  6. Previous efforts Rockwell, Gharib and associates • 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 • No pressure data available • Control by small oscillations of entire wing

  7. Facilities and models • Stability Wind Tunnel with U∞=40 m/s Re≈106 • 44” span trapezoidal wing • Pressure taps • Seven-Hole Probes • New: 3-D Particle Image Velocimetry (PIV)

  8. The oscillating mechanism and laser positioning feedback mechanism.

  9. Flow control with Oscillating mini-flap (AOA=10 degrees)

  10. Comparison with NACA Report • Circular-arc airfoil with leading and trailing edge flaps

  11. Sharp-edged wing with the leading –edge attachment that houses the rotating cylinder and the accumulator chamber.

  12. No Sweep =13° =9°

  13. System of coordinates

  14. Facilities and models • Water Tunnel with U∞=0.25 m/s Re≈32000 • CCD camera synchronized with Nd:YAG pulsing laser • 8” span trapezoidal wing • Particle Image Velocimetry (PIV) • Flow visualization

  15. 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

  16. 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

  17. PIV results • Streamlines and vorticity contours along a plane parallel to the stream half way outboard (left) and detail of field (right).

  18. PIV results (cont.) • 7º AOA

  19. PIV results (cont.) • 13º AOA

  20. PIV results (cont.) • 25º AOA

  21. Facilities and models • Stability Wind Tunnel with U∞=40 m/s Re≈106 • 44” span trapezoidal wing • Pressure taps • Seven-Hole Probes • New: 3-D Particle Image Velocimetry (PIV)

  22. Pressure Distributions along the span

  23. Pressure profiles; Re=106 y/s=0.335

  24. Pressure profiles; Re=106 =7° =13°

  25. Pressure profiles; Re=106 =17° =21°

  26. Trefftz Planes, =13° , Re=106 Axial velocity Vorticity

  27. Trefftz Planes at Stability, =21°, Re=106 Axial velocity Vorticity

  28. LE Actuation, =13°, Re=350,000 Oscillating mini-flap y/s=0.092 y/s=0.33

  29. LE Actuation, =13°, Re=350,000 y/s=0.56 y/s=0.66

  30. Pressure ports location

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

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

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

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

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

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

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

  38. Flow animation for planes A-D

  39. Conclusions • Mini-LE flap and unsteady jet equally effective • Unsteady fully-separated wakes can be controlled: increase of lift • Diamond-Planform Wing stalls: *as delta wing at lower angles of attack (7°~15°) *2-D wing at larger (17°). • Spanwise blowing could be effective actuation

  40. Complex Thermo Fluid Systems Laboratory • Established Fall’03 • ~1200 ft2 (lab) • ~800 ft2 (office space) • ~15 graduate students (>50% PhD) • ~10 undergrad students • State-of-the-art experimental and computational capabilities Graduate Students Ali Etebari (PhD) Olga Pierrakos (PhD) Mike Brady (PhD) John Charonko (PhD) Karri Satya (PhD) Chris Weiland (PhD / MS) Vlachakis Vass. (MS) Alicia Williams (MS) Patrick Leung (MS) Chris Mitchie (MS) Don Barton (MS) *Jose Rullan (PhD) *Hugh Hill (MS/PhD) *Jerrod Ewing (MS) *Andrew Gifford (PhD)

  41. Research Areas Cavitating flows Sprays-Atomization Aerodynamics Laminar and Turbulent Wall Bounded Flows Experimental Methods Optical Diagnostics Sensors Mixing in Multi-Phase Flows Cell-Flow Interaction Cardiac flows Arterial flows

  42. DPIV • In-house developed DPIV software. Capabilities Include: • Extensive image analysis tools, dynamic masking, image operations etc • Stereo-DPIV • Hierarchical super-resolution DPIV-several algorithms • Particle tracking • Novel sub-pixel interpolation schemes • Reduce peak locking • Improve sub-pixel accuracy • Image based particle sizing • Tools for poly-dispersed multi-phase flows

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