DIY Schlieren Flow Visualization
This page documents my experiments with making a Schlieren flow visualization. It was featured on instructables.com.
The best setup worked using these $9 page magnifiers,
and a little LED-light keychain. Thanks
Eli for suggesting
that I use lenses.
This is a photo of what the setup looks like from the side. The candle or air you want to look at is in the center, the magnifiers are spaced about 4 feet apart. The camera is behind one magnifier, skewed a little and the LED light source is hidden behind the other magnifier.
Here is a little diagram of the setup. Note that the camera skew is not exaggerated, it is about what it needs to be in order for the Schlieren visualization to work.
It takes a lot of care to get the camera in the right position, just at the focal point of the of the second magnifier. Below is a video showing that process of positioning the camera.
[coming soon]
Below is another video with some extended footage from the setup.
Below you can see the LED light taped to the side of the tripod... not so exact, but even a simple setup like this worked pretty well.
Later I used a higher table which allowed me to rubber-band the light on to the tripod.
Parabolic and even spherical mirrors can both be used to create a super Shlieren effect. Unfortunately they cost $60-$300 dollars for mirrors of varying quality. Given my love of converting TV's into productive use -> I tried to turn an old DirectTV dish into a massive parabolic mirror. This picture shows how far I made it – by covering it with a mylar sheet, sealing the outer rim with tape and placing the vacuum cleaner up against a small hole in the back of the dish. I had several plans for how to remove air pockets, but then Eli suggested I just use lenses.
Another method I used, which actually worked pretty well is what I called the poor mans Schlieren imaging. I made these by taking the difference between two consecutive photos, one with the candle burning and another with the candle out. The background was a computer printout of noise with a 1/f^2 spectrum (so its scale free).
The guys over at Penn State University made a humongous Schlieren visualization setup, basically the size of a building and the resulting pictures are totally awesome:
mne.psu.edu/psgdl/FullScaleSchlieren.pdf (and a web version).
This is a photo of what the setup looks like from the side. The candle or air you want to look at is in the center, the magnifiers are spaced about 4 feet apart. The camera is behind one magnifier, skewed a little and the LED light source is hidden behind the other magnifier.
Here is a little diagram of the setup. Note that the camera skew is not exaggerated, it is about what it needs to be in order for the Schlieren visualization to work.
It takes a lot of care to get the camera in the right position, just at the focal point of the of the second magnifier. Below is a video showing that process of positioning the camera.
[coming soon]
Below is another video with some extended footage from the setup.
Below you can see the LED light taped to the side of the tripod... not so exact, but even a simple setup like this worked pretty well.
Later I used a higher table which allowed me to rubber-band the light on to the tripod.
Previous attempts
Parabolic and even spherical mirrors can both be used to create a super Shlieren effect. Unfortunately they cost $60-$300 dollars for mirrors of varying quality. Given my love of converting TV's into productive use -> I tried to turn an old DirectTV dish into a massive parabolic mirror. This picture shows how far I made it – by covering it with a mylar sheet, sealing the outer rim with tape and placing the vacuum cleaner up against a small hole in the back of the dish. I had several plans for how to remove air pockets, but then Eli suggested I just use lenses.
Another method I used, which actually worked pretty well is what I called the poor mans Schlieren imaging. I made these by taking the difference between two consecutive photos, one with the candle burning and another with the candle out. The background was a computer printout of noise with a 1/f^2 spectrum (so its scale free).
Fun links
The guys over at Penn State University made a humongous Schlieren visualization setup, basically the size of a building and the resulting pictures are totally awesome:
mne.psu.edu/psgdl/FullScaleSchlieren.pdf (and a web version).
Have fun!
Let me know if you have questions or comments. Contact.