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Definitions
Component—A fluid that is immiscible with other fluids, such as, air, water, and oil.
Mixture—Fluid created by the combination of all the components in a volume or at a boundary.
Phase Mass—Total mass of a component within a selected volume.
Phase Volume—Total volume of component within a selected volume.
Mass Fraction—Mass of a component divided by the total mass within a selected volume.
Volume Fraction—Volume of a component divided by the total volume.
Contact Angle—A contact angle of α = 0 corresponds to full wetting, such as hydrophilic. A contact angle of α = 180 corresponds to no wetting, such as hydrophobic. A contact angle between 0 and 180 corresponds to partial wetting.
α=0 : Full Wetting
0<α<180 : Partial Wetting
α=180 : Phobic
Weber Number—Strength of momentum relative to surface tension. A small Weber number, We, means that the surface tension forces are relatively strong compared to the momentum.
equation 2.52
where,
 ρ density (kg/m3) U∞ free stream velocity (m/s) L representative length scale (m) σ surface tension (N/m) V fluid velocity
Bond Number (Bo) or Eötvös Number (Eo)—Strength of gravity relative to surface tension. A small Bond number or Eötvös number means that the surface tension forces are relatively strong compared to gravity.
equation 2.53
where,
 ρ density (kg/m3) g gravity L representative length scale (m) σ surface tension (N/m)