Suppose a closed tank does not have any pressure relief system and is set to drain from the bottom. It is said that because the headspace pressure drops as the liquid level goes down, the tank will not properly drain.
However, in real situations, I would guess air bubbles start to form in the bottom hole and rise to equilibrate pressure and allow the liquid to drain. I think this ends up depending on the rate of formation and motion of the bubbles which are affected by the geometry and fluid and so on. Is there a systematic way of looking at this? How do you work it out on paper?