Using a schlieren imaging system to see fluid flow

A schlieren imaging system allows one to see things that are normally invisible. The way such a system works is to use a lens or a spherical mirror to focus a point light source onto a thin metal wire so that none of the light is transmitted into a camera that sits behind the wire. With this setup, any density changes in the air will refract the light coming from the source, deflecting it past the wire light block and into the camera. In this way, any density changes in the air will become visible in the camera, allowing one to observe the effects of temperature or pressure changes in the air. In this presentation, I will describe the details of an off-axis single-mirror schlieren system and discuss several experiments that reveal spectacular fluid motion that is normally hidden from view.