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Shockwave formation on the wing. Is this diagram correct?
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. |
#2
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Shockwave formation on the wing. Is this diagram correct?
"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. |
#3
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Shockwave formation on the wing. Is this diagram correct?
"xerj" wrote in message
... 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? Following the custom of this ng, I shall now post even though I have no deep knowledge of the topic and no qualifications to comment on cartoons. The airflow forward of the critical point is supersonic, faster than the speed of sound. Therefore, the pressure wave propogates rearward relative to its point of generation. Aft of the critical point, airflow is subsonic, slower than the speed of sound. Sound pressure waves propogate forward of their point of generation. At the critical point, the pressure wave is a standing wave, propogating such that the wave front remains tanget to a line through the critical point. Each successive wave cycle at the critical point reinforces the preceding waves. Sponge Bob Squarepants then goes on to say: As to the wave frequencies, the effect is similar to Doppler shift. The pressure wave center moves relative to the airfoil. Forward of the critical point, the center of pressure moves rearward away from their point of generation. Versa for points rear of the critical point, in subsonic flow. It really does become very clear when they present it this way, in primary colors. |
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