What is the science of mixing things and are there any great explainers?

December 10, 2022 11:05 AM

I've always been fascinated by mixing particles and fluids... How many turns of a spoon does it take to "totally" mix dough's dry ingredients? If you switch to a new brand of litter by gradually adding new, how long until the last of the old is still in the bin? What is the science that researches this, and are there any fun IRL or online content to follow?

I'm hoping there are some fun, niche areas of mixing that I can follow.

For example, I really like the subgenre of paint mixing guess videos, but I am less interested in the *color* that results from the mixing, and more interested in the physical aspects of it.

I bet I i would like to learn about friction, viscosity, particle size, etc. I bet there's some really interesting content from, like, snack mix manufacturers who have figured out the right way to mix trail mix without damaging fragile nuts.

Also - crowd mixing, how do people act as particles when they are milling about? Do animals mix their herds and flocks? How do the stones in sedimentary rocks get mixed together? Are there things where, if you let them sit, mix automatically? Or, even when you try to mix them, stay separate? (Already know about oil and water, haha.)

Note that I'm not really looking for cooking vids, recipes, or anything else unless they specifically talk about the physics, technology, and science of mixing.

Cheers!

posted by rebent to Science & Nature (7 answers total)

Some good, but technical references if you're into the actual engineering aspects:
intro article
all the technical info you could ever want

And the background theory to diffusion and the random walk model:
diffusion and random walks
Fick's law
posted by Jobst at 11:53 AM on December 10, 2022 [2 favorites]

Wikipedia's article on granular material can help you get a list of topics and a better handle on terminology.

In there eg the Brazil Nut Effect is mentioned, wherein things can sort/un mix due to vibration.
posted by SaltySalticid at 12:58 PM on December 10, 2022 [1 favorite]

Here's a nice article from Physics Today, which is aimed at undergraduate physics students.
posted by BrashTech at 1:53 PM on December 10, 2022

See also on Wikipedia their nice page on Mixing (process engineering) there's some cool stuff there about mathematical models, and the danger of unmixing when you try to mix too much.
posted by SaltySalticid at 5:12 PM on December 10, 2022

The cat litter problem could come down to a dilution equation, assuming the litter is completely mixed when the new is added. But cats are more random than entropy so that whole idea is useless.
posted by JoeZydeco at 6:46 PM on December 10, 2022

You might like the question of how many shuffles does it take to fully randomize a deck?

(Seven is enough, for a certain definition of "fully".)
posted by away for regrooving at 7:01 PM on December 10, 2022

I had a particles/ fluids app on my android phone, fun and interesting, there's an ios version.
posted by theora55 at 9:35 AM on December 11, 2022