Schlieren Imaging Setup
Schlieren imaging is a excellent method of visualizing gasseous fluid flow by providing visual contrast based on minute changes in a fluid's refractive index (often due to temperature and density). I built two different setups as an initial proof of concept then a larger system for laser welding plume imaging.
Version 1
For a long time, I had heard of Schlieren imaging and thought that it would be a very interesting experiement to setup and potentially a highly useful tool to have. Eventually these two factors came together when it was selected as a potentially critical tool for imaging the laser welding plume and using this data for multiphysics model calibration. Version 1 was constructed almost entirely from spare parts in my personal stash. It was built from aluminum extrusion with custom designed mounts for the parabolic mirror, point light source (approximated with a pinhole over an LED), and camera or phone mount. Additionally, an adjustable knife edge was built from spare parts from a scrapped 3d printed that allowed fine adjustment of the knife position with a screw. This initial system proved highly effective and was used to image convective heat flow and fast moving air flows, such as that from a dust blower.
Version 2
Version 2 was built as a part of potential future graduate research. It utilized larger mirrors (6" instead of 3") for a larger window and was setup in a laser welding lab for laser plume imaging. The first attempt used a phone camera but after this preliminary testing, a phantom high speed camera was used for imaging at >5000 fps. This system proved highly effective as a first prototype, though funding did not allow further testing.
