Transcript Post Stall flow control

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.)

Two basic elements of this
lab
*sharp-edged wings
* swept wings

Low-sweep wings stall like
*unswept wings or
*delta wings
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)
The oscillating mechanism and laser positioning
feedback mechanism.
Flow control with Oscillating mini-flap (AOA=10
degrees)
Sharp-edged wing with the leading –edge attachment that houses
the rotating cylinder and the accumulator chamber.
Pressure Distributions along the span
Pressure profiles; Re=106
y/s=0.335
Trefftz Planes, =13° , Re=106
Axial velocity
Vorticity
Trefftz Planes at Stability, =21°, Re=106
Axial velocity
Vorticity
Pressure ports location
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
PIV results
 Streamlines and vorticity contours along a plane
parallel to the stream half way outboard (left)
and detail of field (right).
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