Milk

Hanging out and relaxing tonight, I got a little thirsty. Poured myself a glass of milk. I have a tall milk glass, so I poured it quickly, meaning that I gave the fluid a higher velocity than normal. (Yes, I said milk glass. I only drink milk out of it. It is the perfect size for what I regard to be a good-sized glass of milk. Maybe I will measure it one day.) I noticed that the stream of milk appeared to "twist" as it left the jug and fell into the glass. Also I noticed something I probably hadn't bothered to notice before: as the milk filled the glass, it only slightly splashed. Compared to filling a cup of water, the milk was rather silent.  I poured the milk back in order to try it again. Honestly, I don't think in all of my years I have ever poured milk back into the jug. Interestingly enough, it is harder to pour the milk back into the jug than to do the opposite, which also required more precision than was necessary before, which meant that the milk had to have a lower velocity so that I didn't spill it. I still spilled some, of course. Did this slower moving fluid perform similarly to the first time I poured the milk? Nope. It ran in a stream that was pretty uniform, narrowing as it left the glass and ran into the jug, like when you barely turn on the kitchen faucet.Filling my glass again, I started off with a higher velocity stream and ended with a lower velocity stream, noting the change from the twisted stream to the narrow one as I slowed down the flow.

The stream of particular interest had symmetry and order, characteristic of laminar flow. 2% milk's viscosity is reported to be 1.7 times that of water at 30C and 2.6 times that of water at 0C (from Milk by Paul Gustav Heinemann), which explains why milk slides down your throat while water just splashes on down the hatch.