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Supersonic motion: no backward propagating shock waves

  1. Jan 21, 2014 #1
    There was a recent thread (now closed) where I claimed that a body accelerating beyond the speed of sound emits a shock wave that propagates spherically backward in the rear hemisphere.

    I have reviewed literature on fluid dynamics and it is quite clear to me now that I was wrong. There is no backward-propagating shock waves, spherical or otherwise.

    It might perhaps be interesting for the participants of the discussion why I had that idea. In fact, in one message I revealed my underlying reasoning, even though I did not expand on that. My chief mistake was in thinking that every point of a supersonic body excites shock waves, which then propagate spherically in all directions. That is not correct. Every point of a body moving in a fluid, super- and subsonically alike generates sonic pressure waves; in some directions, in supersonic motion, these sonic pressure waves interfere and form shock waves, not everywhere and certainly not in the rear.

    It is not clear why I thought that pressure waves were always shock waves in supersonic motion. That seems very strange to me in retrospect. Either way I am happy that I have got rid of that misconception and I thank everyone who participated in the thread.
  2. jcsd
  3. Jan 21, 2014 #2


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    Science Advisor

    Glad to hear that voko. Maybe the mods can merge this thread into the old closed one.
  4. Jan 21, 2014 #3


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    Staff: Mentor

    Thread closed temporarily for Moderation...

    Thread re-opened. This is an allowed continutaion of the previous (now locked) thread.
    Last edited: Jan 21, 2014
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