Segment V11.2: Compressible Flow Visualization

(Related to Textbook Section 11.3 - Categories of Compressible Flow)

The speed of light in a gas is a function of the gas density. This allows the use of a Schlieren optical system to visualize compressible flows. An arrangement of lenses, mirrors, and a knife edge can deflect the light rays and produce images that show these density differences.

A very sensitive, large-field Schlieren apparatus is used to reveal the plume of warm, lower density air shed by the human body. Also shown are the density variations that result from the complex oblique shock and expansion waves in a supersonic jet of air issuing from a nozzle at the right. (Video courtesy of Professor G. S. Settles, Director, Gas Dynamics Lab, Penn State University.)