Capillary Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Capillary number, abbreviated as Ca, a dimensionless number, representing the relative effect of viscous forces against the surface tension between a liquid/gas or liquid/liquid interface.  It is the ratio of viscous forces to surface tension forces.

Capillary number formula

 $$\large{ Ca = \frac { \mu \; v } { \sigma } }$$

Where:

$$\large{ Ca }$$ = Capillary number

$$\large{ \mu }$$  (Greek symbol mu) = dynamic viscosity

$$\large{ \sigma }$$  (Greek symbol sigma) = shear tension

$$\large{ v }$$ = velocity of fluid