Hello,
I'm currently doing 3D mixing in a computer programme called Ansys. I have a cylinder full of water, featuring a square cuboid of calcium (the rectaungular cuboid is a stirrer bar, and the smaller cylinder is a mixing zone. I have gravity defined as the standard 9.81 m/s2 downwards) :
I have the mixing set at 60 rpm at the moment.
I find that, after 2.5 minutes, my calcium is down around the bottom (this is a volume fraction graphic, with more blue meaning higher fraction of water, and as the colour leans into red, you have more calcium) :
Then, as the mixing continues, the homogeneity of the entire cylinder stabilises much more (This is about ten minutes in. I've calculated that 3.4671e-04 throughout the cylinder is perfectly homogenous, so it's very close now) :
My question (a basic mechanical/chemical one, I hope) is, why does the calcium initially "stick" to the bottom, despite being set as a cuboid a bit above the bottom at zero seconds, and then is "happy" to mix as time increases?