Timeline for How does a shockwave form from a subsonic upstream?
Current License: CC BY-SA 4.0
7 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Oct 31, 2023 at 20:25 | comment | added | James | You’re super clever, thank you rob!! | |
| Oct 31, 2023 at 20:25 | vote | accept | James | ||
| Oct 31, 2023 at 20:04 | comment | added | Rob McDonald | @James shockwaves always happen quickly - otherwise they wouldn't be a shock. Disturbances in a flow travel at the characteristic wave speed. For this kind of problem, that is the speed of sound. When the flow is faster than the speed of sound, that means that disturbances (information) can not flow upstream. So, when the flow encounters something (downstream) that requires a change (a blockage, a turn, a pressure gradient), the flow must react abruptly. Conversely, in subsonic flow, the disturbance can propagate forward such that it can be 'felt' early and a gradual adjustment can be made. | |
| Oct 31, 2023 at 19:23 | comment | added | James | Hello, thank you for the reply. So the adverse pressure gradient is like the catalyst that makes it jump from say M=1.3 (before the shockwave) to subsonic please? But how does it make the shockwave happen so quick please? | |
| Oct 31, 2023 at 18:00 | comment | added | Rob McDonald | The flow first gradually accelerates to supersonic. Then it encounters an adverse pressure gradient that wants to cause it to slow down. However, information can not propagate forward in a supersonic flow, so a shock is triggered. There is a ton of information on shockwaves available online and in books. Keep looking. | |
| Oct 31, 2023 at 17:26 | comment | added | James | Hello! But how does the shockwave actually form in flow that is originally subsonic (but high speed like M=0.9) please? I couldn’t find a nice explanation of shockwaves online | |
| Oct 31, 2023 at 17:03 | history | answered | Rob McDonald | CC BY-SA 4.0 |