Capillary number

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

: ext{Ca} stackrel{mathrm{def{=} frac{mu v}{sigma}

where mu is the viscosity of the liquid, v is a characteristic velocity and sigma 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.

ee also

* Bond number
* Capillary pressure


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