The Weber number (`W_e`) is a measure of fluid's inertia compared to its surface tension where there is an interface between two different fluids. `W_e` is dimensionless.
`W_e` is often used to analyze thin film flows and the formation of droplets and bubbles.
`W_e` is given by `W_e` = `rho v^2 l / sigma`
where
`rho` is the density of the fluid (typically kg/m3)
v is the velocity of the fluid (typically m/s).
l is its characteristic length, typically the droplet diameter (typically m).