Stokes' Formula

Viscosity force acting on a smooth sphere.

Stokes' Formula

The force of viscosity acting on a smooth sphere in stream line motion can be expressed with Stokes' formula:

F = 6 π η r v (1)

Where:

  • F = force (N)
  • η = viscosity of fluid (Pa·s)
  • r = radius of sphere (m)
  • v = relative velocity between fluid and sphere (m/s)
Calculator

Inputs

Results

Viscosity Force (F)-- N
ParameterSymbolValueUnit
Viscosity of fluidηinputs.viscosityPa·s
Radius of sphererinputs.radiusm
Relative velocityvinputs.velocitym/s
Viscosity ForceF6 * 3.14159265 * inputs.viscosity * inputs.radius * inputs.velocityN