1. Aerospace Engineering Iowa State University 311L Schlieren & Shadowgraph Methods Aerospace Engineering 311L

2. Aerospace Engineering Iowa State University 311L Models of Light m/s Physical (wave) model Wave Peaks Geometric model Light Rays

3. Aerospace Engineering Iowa State University 311L Light From a Point Source

4. Aerospace Engineering Iowa State University 311L Speed of Light in a Medium Index of Refraction: c = speed of light in the medium Typical values: Mediumn = c o /c Air1.0003 Water1.33 Crown glass1.52 Plexiglas1.51 Diamond2.42 For gases: = gas density k = 0.23 cm 3 /g for air

5. Aerospace Engineering Iowa State University 311L Light Refraction Medium 2 Medium 1 Snell’s Law:

6. Aerospace Engineering Iowa State University 311L Example, Refraction in Water Water Surface Pole

7. Aerospace Engineering Iowa State University 311L Lenses Focus

8. Aerospace Engineering Iowa State University 311L Lenses Point Source

9. Aerospace Engineering Iowa State University 311L Direct Shadowgraphy Point Source Bubble of high density gas

10. Aerospace Engineering Iowa State University 311L Shadowgraph Image

11. Aerospace Engineering Iowa State University 311L Some Math x y z or

12. Aerospace Engineering Iowa State University 311L The Basic Schlieren System Point Source

13. Aerospace Engineering Iowa State University 311L The Real Schlieren System Extended Source

14. Aerospace Engineering Iowa State University 311L Schlieren Image

15. Aerospace Engineering Iowa State University 311L Schlieren vs. Shadowgraph Displays a mere shadow Shows light ray displacement Illuminance level responds to No knife edge used Displays a focused image Shows ray refraction angle,  Illuminance level responds to Knife edge used for cutoff Shadowgraph Schlieren

16. Aerospace Engineering Iowa State University 311L Mirrors

17. Aerospace Engineering Iowa State University 311L ISU’s Z-type Schlieren System 1 st Field Mirror 2 nd Field Mirror Screen/Instrument Panel Light Source Test Section Knife Edge

18. Aerospace Engineering Iowa State University 311L Light Source Lamp Condenser Lens Section A-A A-A

19. Aerospace Engineering Iowa State University 311L Setting Up The Schlieren System Step 1: Find the focal length of the field mirrors Focal Length

20. Aerospace Engineering Iowa State University 311L Setting Up The Schlieren System Step 2: Set up the first field mirror 1 st Field Mirror Light Source Test Section

21. Aerospace Engineering Iowa State University 311L Setting Up The Schlieren System Step 3: Set up the second field mirror 1 st Field Mirror Light Source Test Section 2 nd Field Mirror Screen/Instrument Panel

22. Aerospace Engineering Iowa State University 311L Setting Up The Schlieren System Step 4: Set up the knife edge Focus the source image on the knife Adjust the cutoff Obtain a uniform darkening of the image

23. Aerospace Engineering Iowa State University 311L Uniform Darkening Knife edge too close to second field mirror Knife edge too far from second field mirror Uniform darkening

24. Aerospace Engineering Iowa State University 311L Some Notes The angle between the illuminator axis and the collimated beam should be kept to a minimum –Coma: Smearing of the mirror focus into a comet shape (cancelled out by tilting the mirrors in opposite directions, i.e. z-type system) –Astigmatism: Changes the focus into two short lines perpendicular to each other (limited by orienting the knife edge the same as the light source) A sheet of white paper is a good alignment tool A threaded bolt works well as a focusing tool

25. Aerospace Engineering Iowa State University 311L References G.S. Settles, Schlieren & Shadowgraph Techniques, Springer-Verlag, 2001. D.C. Giancoli, Physics for Scientists & Engineers, Prentice Hall, 1988.