- #1
voko
- 6,054
- 391
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.
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.