# Weber Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Weber number, abbreviated as We, a dimensionless number, is used in fluid mechanics is often useful in analysing fluid flows where there is an interface between two different fluids, especially for multiphase flows with strongly curved surfaces.  It is a measure of the relative importance of the fluid's inertia compared the its surrface tension.  The reason this number is important is it can be used to help analyze thin film flows and how droplets and bubbles are formed.

## Weber number formula

 $$\large{ We = \frac{ \rho \; v^2 \; l_c }{\sigma} }$$

### Where:

 Units English Metric $$\large{ We }$$ = Weber number $$\large{ dimensionless }$$ $$\large{ l_c }$$ = characteristic length $$\large{ ft }$$ $$\large{ m }$$ $$\large{ \rho }$$  (Greek symbol rho) = density $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$\large{ \sigma }$$  (Greek symbol sigma) = surface tension $$\large{\frac{lbf}{ft}}$$ $$\large{\frac{N}{m}}$$ $$\large{ v }$$ = velocity of fluid $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$ 