Capillary number

In fluid dynamics, the capillary number represents the relative effect of viscous forces versus surface tension acting across an interface between a liquid and a gas, or between two immiscible liquids. It is defined as

Additional recommended knowledge

Daily Sensitivity Test

Weighing the right way

Don't let static charges disrupt your weighing accuracy

where μ is the viscosity of the liquid, v is a characteristic velocity and σ is the surface or interfacial tension between the two fluid phases.

For low capillary numbers (a rule of thumb says less than 10 ^{− 5}), flow in porous media is dominated by capillary forces.

See also

• Bond number
• Capillary pressure