5 ms·
The conditions to reach sonic flow are surprisingly modest! It's fully characterized through the pressure ratio between high-pressure reservoir (here: inside o
by bernulli 4y ago
The conditions to reach sonic flow are surprisingly modest!
It's fully characterized through the pressure ratio between high-pressure reservoir (here: inside of bottle) and low-pressure surroundings, and a parameter characterizing the molecular structure, the isentropic exponent.
For diatomic molecules (our air), the isentropic exponent is 1.4, and the critical pressure ratio at which Mach 1 will be reached is ~0.5, i.e. as long as the high pressure is twice as high as the surrounding pressure, the flow will reach the speed of sound. For more complex molecules the isentropic exponent approaches 1.1, and for steam 1.14, with a critical pressure ratio of ~0.58.
I.e. when you release air from a >2 bar (30psi) car/bike tire, you have sonic flow right there!
- cevn 4y agoFascinating... I would like to subscribe to your newsletter!
- bernulli 4y agoHaha, thanks! Let me think about this! ;-)
- robonerd 4y agoUnfortunately this seems to be well beyond what the human lungs can do. I found this paper https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1501025/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1501025/ suggesting that the most human lungs can do is about 1 meter of H20, or about a 0.1 bar. So it seems supersonic whistling isn't possible. Oh well.
- Arrath 4y agoI swear my ears beg to differ at the tones some people can reach, ow.