Schlieren Flow Visualization

A really neat technique for visualizing the flow of fluids is called Schlieren flow visualization (pronounced: sh-lear-in). By using either special mirrors or lenses, the density gradients of a fluid can be seen. Examples would be the heat rising from a candle, or the aerodynamics effects of a bullet traveling through the air. This technique is used in wind tunnels and in many other areas of research.

This diagram from NASA shows a typical duel mirror Schlieren setup:

nasa-schlieren

Here are a couple examples of what a Schlieren setup can produce:

schlieren1

And this one:

220px-Schlieren-color-candle-plume

“Schlieren-color-candle-plume” by Settles1 – Licensed under C.C. Attribution 3.0 via Wikimedia Commons