The conditions to reach sonic flow are surprisingly modest!<p>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.<p>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.<p>I.e. when you release air from a >2 bar (30psi) car/bike tire, you have sonic flow right there!
Here is a similar visualisation from Phantom using Schlieren:<p><a href="https://youtu.be/kEw2msVaVy0" rel="nofollow">https://youtu.be/kEw2msVaVy0</a>
Ooh - Figure 4 of the linked PDF shows temperatures as low as -120 Celcius! And thats from a champagne pressure of just 4 bar.<p>Does that imply that a carefully shaped and designed nozzle, combined with slightly higher pressures, attached to a regular air compressor could be used to make liquid nitrogen?
It's amazing how often effects go to supersonic speeds in everyday life. It really makes sense why our hearing is logarithmic, otherwise we'd all be deaf just from a cork popping.
These are some very smart academics who have figured out how to get their institutions to fund their parties, and probably became very popular in their social circles
I can't be the only one wondering this...<p>How many bottles of champagne were purchased for this research, and what was done with their contents afterwards?
This is cool, but thank some higher power I decided against getting a masters / PHD. Imagine years of your life dedicated to understanding how a champagne cork explodes. Nightmare material.