Flow around single particle

Question 1

forces acting on a particle

Answer 1

gravity, buoyancy, drag

Fg = Fb + Fd

Question 2

what is drag force?

Answer 2

sum of pressure drag forces (velocity behind particle close to 0, so pressure forces are high, but can also get edies where velocity is very high so presusre is low, causing pressure drag) and shear drag forces (force as fluid flows around particle)

Question 3

Cd

Answer 3

function of particle Reynold number and sphericity

Question 4

unhindered vs hindered

Answer 4

unhindered = single falling particle

hindered = particles close together (l<10-20dp), or close to wall (dp>0.01distance between walls, or close to ground (l<100dp), there are static forces that reduce the terminal velocity