# Weber Number

## Introduction to the Weber Number

**The Weber Number** is a dimensionless value useful for analyzing fluid flows where there is an interface between two different fluids.

The Weber Number is the ratio between the inertial force and the surface tension force and the Weber number indicates whether the kinetic or the surface tension energy is dominant. It can be expressed as

We = ρ v^{2}l / σ (1)

where

We = Weber number (dimensionless)

ρ = density of fluid (kg/m^{3}, lb/ft^{3})

v = velocity of fluid (m/s, ft/s)

l = characteristic length (m, ft)

σ = surface tension (N/m)

Since the Weber Number represents an index of the *inertial force* to the *surface tension force* acting on a fluid element, it can be useful analyzing thin films flows and the formation of droplets and bubbles.

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