${\alpha }_i$	Phase indicator (phase i)
${\alpha }_{\mathrm{C}}$	Phase indicator (continuous phase)
${\alpha }_{\mathrm{D}}$	Phase indicator (dispersed phase)
γ	Surface tension	N·m−1
δ	Annular liquid film thickness	m
μ	Viscosity	Pa·s
${\mu }_{\mathrm{C}}$	Viscosity of the continuous phase	Pa·s
${\mu }_{\mathrm{D}}$	Viscosity of the dispersed phase	Pa·s
${\mu }_{\mathrm{L}}$	Viscosity of the liquid	Pa·s
ρ	Density	kg·m3
${\rho }_{\mathrm{C}}$	Density of the continuous phase	kg·m3
${\rho }_{\mathrm{D}}$	Density of the dispersed phase	kg·m3
${\rho }_{\mathrm{L}}$	Density of the liquid	kg·m3
${\rho }_{\mathrm{G}}$	Density of the gas	kg·m3