Science & engineering
Stokes settling velocity
Estimate a small sphere’s settling speed and inspect the resulting Reynolds number.
A clear answer. Here’s how.
Balances Stokes drag against buoyancy-corrected weight: V=2r²g(ρparticle−ρfluid)/(9μ). Positive means settling downward; lower-density particles rise. Computes particle Re from the estimated speed and flags when it is not well below one. Assumes an isolated rigid sphere in creeping Newtonian flow; non-spherical, interacting or turbulent settling is unsupported.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Particle radius (mm)
- 0.01
- Particle density (kg/m³)
- 2500
- Fluid density (kg/m³)
- 1000
- Dynamic viscosity (mPa·s)
- 1
Example result
- Signed terminal velocity (m/s)
- 0.000326888333333
- Particle Reynolds number
- 0.00653776666667
- Direction
- Downward
Creeping-flow regime based on the estimated speed.