"xerj" wrote:
On this page, there's an animated diagram (aptly done in shockwave)
about normal shockwave formations:-

http://selair.selkirk.bc.ca/aerodyna...ed/Page2c.html

Something confuses me though. As diagrammed, the red pressure wave at
the rear has a low frequency at the front and a high frequency at the
back. Why would this happen (if indeed it does)? Why is the frequency
HIGHER in the direction that the airflow is moving?

Thanks in advance.

Your question would probably get more informed replies on any of:

sci.physics.computational.fluid-dynamics,
sci.aeronautics, or
sci.mech.fluids.