Flow Control over Swept, Sharp-Edged Wings

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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
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Flow Control Team
P. Vlachos
J. Rullan
J. Gibbs
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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 lt Re lt 10 6
• Conclusions

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Background

• Trapezoidal sharp-edged wings common in todays
  fighter aircraft.
• Little understanding of aerodynamic effects at
  sweeping angles between 30 and 40 AOA.

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Background (cont.)

• Low-sweep wings stall like
• unswept wings or
• delta wings

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Previous efforts Rockwell, Gharib and associates

• 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 number10000
• No pressure data available
• Control by small oscillations of entire wing

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Facilities and models

• Stability Wind Tunnel with U840 m/s Re106
• 44 span trapezoidal wing
• Pressure taps
• Seven-Hole Probes
• New 3-D Particle Image Velocimetry (PIV)

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The oscillating mechanism and laser positioning
feedback mechanism.  
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Flow control with Oscillating mini-flap (AOA10
degrees)
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Comparison with NACA Report

• Circular-arc airfoil with leading and trailing
  edge flaps

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Sharp-edged wing with the leading edge
attachment that houses the rotating cylinder and
the accumulator chamber.
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No Sweep

?13
?9
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System of coordinates
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Facilities and models

• Water Tunnel with U80.25 m/s Re32000
• CCD camera synchronized with NdYAG pulsing laser
• 8 span trapezoidal wing
• Particle Image Velocimetry (PIV)
• Flow visualization

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Time-Resolved DPIV
Sneak Preview of Our DPIV System

• Data acquisition with enhanced time and space
  resolution ( gt 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

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DPIV

• Digital Particle Image Velocimetry System III
  Conventional Stereo-DPIV system with
• 30 Hz repetition rate (lt 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 NdYag
• 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

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PIV results

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

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PIV results (cont.)

• 7º AOA

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PIV results (cont.)

• 13º AOA

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PIV results (cont.)

• 25º AOA

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Facilities and models

• Stability Wind Tunnel with U840 m/s Re106
• 44 span trapezoidal wing
• Pressure taps
• Seven-Hole Probes
• New 3-D Particle Image Velocimetry (PIV)

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Pressure Distributions along the span
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Pressure profiles Re106
y/s0.335
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Pressure profiles Re106

• ?7 ?13

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Pressure profiles Re106

• ?17 ?21

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Trefftz Planes, ?13 , Re106

• Axial velocity Vorticity

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Trefftz Planes at Stability, ?21, Re106

• Axial velocity Vorticity

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LE Actuation, ?13, Re350,000
Oscillating mini-flap
y/s0.092
y/s0.33
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LE Actuation, ?13, Re350,000
y/s0.56
y/s0.66
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Pressure ports location
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Pressure distributions for a130.

• Stations 5-7

• Stations 8-10

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Pressure distributions for a170.

• Stations 5-7

• Stations 8-10

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Vortex Patterns

• Visbal and Gursul call it dual vortex structure

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Results (cont.)

• Plane A, t2T/8,t3T/8

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Results (cont.)

• Plane A, control, t4T/8,t5T/8

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Results (cont.)

• Plane A, control, t6T/8,t7T/8

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Results (cont.)

• Plane D, no control and control

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Flow animation for planes A-D
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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
  (715)
• 2-D wing at larger (17).
• Spanwise blowing could be effective actuation

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Complex Thermo Fluid Systems Laboratory

• Established Fall03
• 1200 ft2 (lab)
• 800 ft2 (office space)
• 15 graduate students (gt50 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)
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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
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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