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# Eötvös number

In fluid dynamics the Eötvös number (Eo) is a dimensionless number named after Hungarian physicist Loránd Eötvös (1848-1919).

Together with Morton number it can be used to characterize the shape of a fluid sphere (air bubble, water drop...). Eötvös number may be regarded as proportional to buoyancy forces divided by surface tension forces.

$\mathrm{Eo}=\frac{\Delta\rho \,g \,L^2}{\sigma}$
• Δρ: difference in density of the two phases, (SI units : kg/m3)
• g: gravitational acceleration, (SI units : m/s2)
• L: characteristic length, (SI units : m)
• σ: surface tension, (SI units : N/m)