Sunday, December 11, 2011 10:05:06 PM
A more accurate name is a vortex tube. Bubble implies the fluid is stationary (that is, not rotating). They can be created with any high velocity burst in a fluid so the volcano one is legit. I'm sure they happen in nature a lot more often but just aren`t visible.
It is impossible for the tube to end within the fluid, as seen when the dolphin splits one in two, and the faster it spins the more stable it is which is probably why the volcano one doesn`t oscillate like the dolphin`s did.
How appropriate this was posted the day before my exam on fluid mechanics (I`m not kidding, Mech Eng graduate school). We watched the dolphin video in class. My prof was a little too excited about it.