A dimensionless number used in momentum transfer in general and bubble/droplet formation and breakage of liquid jets calculations in particular. Proportional to (Inertial force) / (Surface tension force).

We = (D V^{2} rho) / (g_{c} sigma)

We = (D G^{2}) / (g_{c} rho sigma)

g_{c}: dimensional constant, G: mass velocity, D: characteristic length, rho: density, sigma: surface tension, v: velocity

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