I have a headscratcher: Suppose you have a suspension, say sand dispersed in water. Looked at as a bulk, over the whole volume, the density would be higher than water. Do we expect a higher pressure near the botom of the vessel because of this?
Two possible scenarios com to mind: Sand (or another solid) is dispersed and sinking to the ground, sand is dispersed and a mixer addes energy and keeps the sand dispersed. When I try to solve this headscratcher, My thinking goes like this:
- With sinking particles, there's an upward force acting on the particles (friction according to Hookes/Kaskas equation)
- action, reaction, etc. - there's a force acting on the water
- hence there's a higher pressure at the bottom of a suspension, however ...
- in a non equlibrium case, the pressure does not correspond to the bulk density of water + solid, but is somewhat smaller
- In an equilibrium case (mixer), the pressure should be equivalent to pressure according to the bulk density
In most real life cases, a solid will either one or all of ...
- settle quickly
- be not much more dense than the fluid
- be of low percentage of the total volume
...so the effect will be really small
This is my line of thinking so far. If wrong, I'd like to be shown where. If correct, I want confirmation. Either way, I expect answers to be backed up by some authoritative source.
p.s. If my thinking is correct, you could make a nice experiment out of my bullet points 4 & 5.