Why Does Water Un-Smoothly Flow From Certain Containers?

Why does water flow smoothly without bubbling from certain shaped bottles, but not others? Particularly with narrow bottle-necked ones, fluid comes out in bursts, no matter how slowly you pour it - until you reach the halfway point where you can just manage to get a smooth pour.

This ‘gulping’, or unsteady flow is a result of air entering the jug which temporarily halts the flow of the fluid. Now when water is turned over to be poured, the pressure inside the jug drops. When the pressure gets lower than atmospheric pressure, air will force itself into the bottle to bring it back to atmospheric pressure, and only then will the water begin pouring again. As the water flows out, this happens again, and so air flows in and so again until all the water pours out. Now, as we empty about half of the container, some jugs will at that point begin to flow smoothly, and this is because enough air is actually able to enter while water is flowing out, hence eliminating the cessation effect of the water flow. For larger jugs, we tend to see smooth flow, since air can more abundantly flow in. And also, jugs have a pointy mouth so that air can enter from the top bit, while fluid flows downwards. Fascinating!

However, this phenoma is not actually exclusive to water, but is an example of the Rayleigh-Taylor instability between a lighter and heavier fluid, where in this case it is air and water respectively. This effect occurs, for examples, when pouring milk into coffee, in underwater explosions, and in oil and water combinations.