Transcript Flow Visualization - Purdue University

AAE 520 Experimental Aerodynamics
Optical Techniques for Flow
Visualization
• Shadowgraph
• Schlieren
• Interferometer
2 2
 2
2
x
y

gradientsperpendicular toknifeedge
y

All depend of the fact that the speed of light and therefore the
index of refraction varies with the density.
The index of refraction is approximately

  (  )  1  
 ref
  .000292 for air
Purdue University - School of Aeronautics and Astronautics
AAE 520 Experimental Aerodynamics
Shadowgraph
Shocks appear as
a dark line followed
by a light line

Point
Source
of light
deflection
Flow
Purdue University - School of Aeronautics and Astronautics
Viewing
Screen
AAE 520 Experimental Aerodynamics
Shadowgraph
Purdue University - School of Aeronautics and Astronautics
AAE 520 Experimental Aerodynamics
Purdue University - School of Aeronautics and Astronautics
AAE 520 Experimental Aerodynamics
Schlieren Optics
c
a
b’
a’
b
Light
Source
d
Test
Section
Knife
edge
Image
Mask
(knife edge)
Displaced
Image
Image
of
source
d’
c’
Image
of
Test
Section
Knife edge intercepts part of source image
Density gradient causes displacement
of source image
Color Schlieren uses a color in
place of knife edge
Purdue University - School of Aeronautics and Astronautics
AAE 520 Experimental Aerodynamics
Z-folded Schlieren Using Mirrors
Camera
Knife
edge
Test Section
Light
Source
Purdue University - School of Aeronautics and Astronautics
AAE 520 Experimental Aerodynamics
Color Schlieren
Purdue University - School of Aeronautics and Astronautics
AAE 520 Experimental Aerodynamics
Schlieren for Flight Test
Purdue University - School of Aeronautics and Astronautics
AAE 520 Experimental Aerodynamics
Mach-Zender Interferometer
Light
Source
Beamsplitter
Mirror
Mirror
Beamsplitter
Test Section
Purdue University - School of Aeronautics and Astronautics
Image
AAE 520 Experimental Aerodynamics
Purdue University - School of Aeronautics and Astronautics