Work out terminal settling velocity (stokes) instantly with clear inputs, formula shown and shareable results.
Stokes' law balances weight, buoyancy and viscous drag on a small sphere, giving v = (rho(p) - rho(f)) g d^2 / (18 mu). Because diameter is squared, a fine particle settles dramatically more slowly: 100 micron sand in water falls about 9 mm/s, while 10 micron silt takes a hundred times longer. The law only holds while the Reynolds number stays below about one.
Stokes settling velocity
v = (rho(p) - rho(f)) g d^2 / (18 mu)
Validity check
Re = rho(f) v d / mu must be below about 1
Stokes' law overpredicts. Use an intermediate or Newton drag regime correlation instead, which grows more slowly with diameter.
Yes, when the particle is lighter than the fluid. It then rises at the same rate, which is how creaming and flotation are analysed.