Seeing the Invisible: The Beauty of Schlieren Imaging

Video Description

In this video we take an in-depth look at a schlieren imaging system, carefully examining the details to understand exactly how it works. The images obtained using this system are truly spectacular! If you like this video, please share it with others who you think would find it interesting (and by all means subscribe!) You can also support this channel through Patreon: https://www.patreon.com/allthingsphysics. This project was supported, in part, by Dickinson College. A big thanks to Adi Chacko for all his help setting up the schlieren experiments and filming dozens of scenes. I am also indebted to my advisory panel (Lars English, Jeff Forrester, and Brett Pearson) for some very helpful discussions and comments on an early version of this video. And as usual, I owe a huge thanks to my Dickinson colleagues for supporting my efforts, and to Jonathan Barrick for constructing several useful pieces of equipment for this project. Lastly, Ryan Burke did me a big favor by sitting patiently in front of Old West (thanks Ryan!). This project was originally inspired by a paper written by Allen Crockett and Wolfgang Rueckner and published in the American Journal of Physics (https://doi.org/10.1119/1.5042245 ). Anyone interested in learning more about schlieren imaging should consult "Schlieren & Shadowgraph Techniques: Visualizing Phenomena in Transparent Media," by G. S. Settles (published by Springer-Verlag). The ray optics simulation program used in this video can be accessed at: https://phydemo.app/ray-optics/. Music for this video: "Nature Documentary" by AlisiaBeats, downloaded from Pixabay https://pixabay.com/music/modern-classical-nature-documentary-171967/ "Documentary Ambient" by The Mountain, downloaded from Pixabay https://pixabay.com/music/ambient-documentary-ambient-136114/ "Documentary" by Ivan_Luzan, downloaded from Pixabay https://pixabay.com/music/beautiful-plays-documentary-145631/ Chapters: 00:00 Introduction 02:41 Flat mirror 05:37 Spherical mirror schlieren geometry 08:17 Refraction 11:16 A real schlieren system 14:30 Adding colored filters 17:13 What the colors represent 18:50 More schlieren images 20:48 Vortex rings 23:26 Final thoughts Corrections: 19:57 Actually, all we can say for sure is that this gas is *more dense* than the surrounding air. If this gas is air, then we can deduce that it must be colder than the surrounding air. However, these gas dusters contain difluoroethane, which is, indeed, more dense than air, so this is almost certainly the effect we are seeing. Having said that, it is still true that the gas coming out of the gas duster goes through a throttling process and is colder than the surrounding air.