Synthetic schlieren

Synthetic schlieren is a process that is used to visualize the flow of a fluid of variable refractive index.

Named after the schlieren method of visualization, it consists of a digital camera or video camera pointing at the flow in question, with an illuminated target pattern behind.

Pattern matching algorithms can measure this distortion and calculate a qualitative density field of the flow.

The method of synthetic schlieren can be used to observe any flow which has variations in refractive index.

As with the optical schlieren method, the clearest results are obtained from flows which are largely two-dimensional.