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) |