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 Facilities and models Experimental tools (PIV, pressure scanners, 7-hole probes) Actuators   Mini-flaps, pulsed jets Results: 1.

Circular-arc airfoils 2.

3.

4.

Swept wings Flow Control at high alpha 10 4 < Re < 10 6 Conclusions

Background   Trapezoidal sharp edged wings common in today’s fighter aircraft.

Little understanding of aerodynamic effects at sweeping angles between 30 ° and 40° AOA.

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

Previous efforts Rockwell, Gharib and associates      Sweep angle 38.7

º  vortices for triangular planform Flow appears to be dominated by delta wing Interrogation only at planes normal to flow Low Re number~10000 No pressure data available Control by small oscillations of entire wing

Facilities and models      Stability Wind Tunnel with U ∞ =40 m/s Re≈10 6 44” span trapezoidal wing Pressure taps Seven-Hole Probes

New: 3-D

Particle Image Velocimetry (PIV)

The oscillating mechanism and laser positioning feedback mechanism.

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

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Comparison with NACA Report

Circular-arc airfoil with leading and trailing edge flaps

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

No Sweep  =9°  =13°

System of coordinates

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

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

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

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

PIV results (cont.)  7 º AOA

PIV results (cont.)  13 º AOA

PIV results (cont.)  25 º AOA

Facilities and models      Stability Wind Tunnel with U ∞ =40 m/s Re≈10 6 44” span trapezoidal wing Pressure taps Seven-Hole Probes

New: 3-D

Particle Image Velocimetry (PIV)

Pressure Distributions along the span

Pressure profiles; Re=10 6 y/s=0.335

Pressure profiles; Re=10 6  =7°  =13°

Pressure profiles; Re=10 6  =17°  =21°

Trefftz Planes,  =13° , Re=10 6 Axial velocity Vorticity

Trefftz Planes at Stability,  =21°, Re=10 6 Axial velocity Vorticity

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

y/s=0.33

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

y/s=0.66

Pressure ports location

Pressure distributions for α=13 0 .

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Stations 5-7

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Stations 8-10

Pressure distributions for α=17 0 .

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Stations 5-7

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Stations 8-10

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

Results (cont.)

 Plane A, t=2T/8,t=3T/8

Results (cont.)

 Plane A, control, t=4T/8,t=5T/8

Results (cont.)

 Plane A, control, t=6T/8,t=7T/8

Results (cont.)

 Plane D, no control and control

Flow animation for planes A-D

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

Complex Thermo Fluid Systems Laboratory

 Established Fall’03  ~1200 ft 2 (lab)  ~800 ft 2 (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)

Research Areas

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

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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