Timeline for Is my understanding of density/speed correct?
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
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| Jan 17 at 0:48 | comment | added | Wyatt | @RobertDiGiovanni Yeah I kind of visualized it in my mind, which helped. I can definitely see a shockwave acting like a 'wall', which behind it is low pressure. Thanks! | |
| Jan 16 at 23:27 | comment | added | Robert DiGiovanni | probably many theories, but to me a trans or super sonic shockwave is like a moving wall of compressed air, literally leaving a "wake" of lower pressure behind it within its cone. The lower density behind it (and the higher pressure in front) may be one reason why longitudinal stability "diverges" at higher Mach. Good luck with your studies on this very complex subject. | |
| Jan 16 at 21:49 | comment | added | Wyatt | @RobertDiGiovanni hmm good points. One question, why would the pressure be lower behind a shockwave? | |
| Jan 16 at 21:24 | comment | added | Robert DiGiovanni | Though one might see something like that at ... the exhaust of a jet engine. More food for thought. | |
| Jan 16 at 21:19 | comment | added | Robert DiGiovanni | density where? I believe they are talking about phenomena behind the shockwave. But is density vs velocity a function of air itself? Or is it (as pressure, Bernoulli) that a moving air (or water) stream draws air away from a surface, creating lower pressure, ergo density? Air simply moves from high pressure to low. To have a significant change in density (along the path of the airstream, within a few meters) would require one heck of a pressure differential. | |
| Jan 16 at 18:52 | comment | added | Wyatt | @RobertDiGiovanni hmm okay. I came across this answer, and if you look at the bottom of it, you'll see a part about density. Could you explain what it means, because it says "A speed increase is always coupled to a decrease in density." which is confusing because at this point I'm not sure if density increases or decreases with speed. Thanks | |
| Jan 16 at 18:35 | comment | added | Robert DiGiovanni | I know it can be confusing because, even in a wind tunnel, "wind flow" is not entirely accurately portrayed (but good enough to get some solid research done). In reality it's the air reacting with the wing in motion. This is why they say air isn't compressed (at lower Mach), it just gets moved out of the way. The Gedanken experiment seemed to deal with pressure differences behind the shockwave at transonic speeds. This took a lot of years for many people to figure out. | |
| Jan 16 at 16:34 | comment | added | Wyatt | @RobertDiGiovanni ah okay I see. So I’m kind of confused about how the Gedankin experiment answer ‘works’ because you made a good point about pressure vs. temperature. | |
| Jan 16 at 10:02 | comment | added | Robert DiGiovanni | Going back to basics may help here. If air molecules "bounce off each other less", the air is cooler. Pressure is a function of Density and Temperature. I would not conflate this with Trans-sonic "Gedanken experiments" for now. | |
| Jan 16 at 0:01 | history | edited | Wyatt | CC BY-SA 4.0 |
edited title
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| Jan 15 at 6:47 | answer | added | Chris | timeline score: 2 | |
| Jan 14 at 22:25 | history | asked | Wyatt | CC BY-SA 4.0 |