A dimensionless group used in analysis of fluid flow that characterizes the ratio of gravitational forces to surface or interfacial tension forces. The Eötvös number is denoted Eo and is equivalent to the Bond number (Nb = Bo).
The Eötvös or Bond number is given by
Eo = Nb = Bo = (Δρ g b2) / σ,
Eo = Eötvös number
Nb = Bo = Bond number
Δρ = density difference between the two phases
g = acceleration due to gravity
b = a characteristic length scale of the flow geometry
σ = surface or interfacial tension.