Purdue University - School of Aeronautics and Astronautics AAE 520 Experimental Aerodynamics Optical Techniques for Flow Visualization Shadowgraph Schlieren Interferometer 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

Purdue University - School of Aeronautics and Astronautics AAE 520 Experimental Aerodynamics Shadowgraph Point Source of light Viewing Screen Flow deflection Shocks appear as a dark line followed by a light line

Purdue University - School of Aeronautics and Astronautics 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 Light Source Test Section Image of source Image of Test Section Mask (knife edge) a b c d a’ b’ c’ d’ Knife edge Image Displaced Image 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 Light Source Test Section

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 Test Section Light Source Beamsplitter Mirror Image

Purdue University - School of Aeronautics and Astronautics AAE 520 Experimental Aerodynamics