The Prandtl-Glauert Singularity

Source: Webstie

http://www.kuriositas.com/2011/02/prandtlglauert-singularity-amazing-jet.html

 

It’s an amazing site – a cone of vapor appearing around an aircraft which is travelling at transonic speed.  Known as the Prandtl–Glauert Singularity this astonishing effect simultaneously widens the eyes and drops the jaw. Yet how does it occur?