Capillary Number

Compute the relative importance of viscous forces to surface tension.

visual calculatorMultiphase Flow

Read the flow shape before trusting the number.

This page turns a CFD setup into regime, scale, and dominant-effect cues. Adjust the calculator below and compare the moving graphic with the computed result.

input scale

model

check

capillarysurface tensionmultiphase

formula

KaTeX rendered

\begin{aligned}\text{Ca = mu U / sigma}\end{aligned}

ASCII source

Ca = mu U / sigma

mu (Pa·s)U (m/s)sigma (N/m)

0.0139

regime

mixed balance

Capillary number is especially useful for coating flows, microfluidics, and interface-capturing problems with moving contact lines.

capillary surface tension multiphase