I'm trying to understand the mechanism behind cold crashing. When cold crashing, you cool the fermented brew, yeast and suspended solids settle. With my first cider, a very turbid bottle visible cleared in a day or two. Why do solids settle whan cooling?
Generally, sedimentation happens continously and is faster at low viscosities of the suspending liquid. Cooler water is actually more viscous so you'd expect slower sedimentation. Another purely physical explanation would be that with colder temeperatures there's less diffusive mass transport and the actual sedimentation dominates. But the temperature difference between ordinary storage and cold crashing is not that much, and in other sedimeantion applications we don't talk about temperature at all. So I assume it's no purely physcial process.
So I would assume that by cooling, we immobilize the yeast cells leading to them sedimenting at the bottom, but that's pure conjecture on my part and I'd like to hear a detailed explanation of the hows and whys of cold crashing.