Multiphase flow

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In fluid mechanics, multiphase flow is simultaneous flow of: – Materials with different states or phases (i.e. gas, liquid or solid). – Materials with different chemical properties but in the same state or phase (i.e. liquid-liquid systems such as oil droplets in water).

Each of the phases is considered to have a separately defined volume fraction (the sum of which is unity) and velocity field. Conservation equations for the flow of each species (perhaps with terms for interchange between the phases) can then be written down straightforwardly.

The momentum equation for each phase is less straightforward. It can be shown that a common pressure field can be defined and that each phase is subject to the gradient of this field, weighted by its volume fraction. Transfer of momentum between the phases is sometimes less straightforward to determine, and, in addition, a very light phase in bubble form has a virtual mass associated with its acceleration. (The virtual mass of a single bubble is about half its displaced mass).

These terms, often called constitutive relations, are often strongly dependent on flow regime.

See also[edit]


  • Crowe, Clayton; Sommerfield, Martin; Yutaka, Tsuji (1998). Multiphase Flows with Droplets and Particles. CRC Press. ISBN 0-8493-9469-4. 
  • Wang, M. Impedance mapping of particulate multiphase flows, Flow Measurement and Instrumentation, (2005) Vol. 16
  • Crowe, Clayton (2005). Multiphase Flow Handbook. CRC Press. ISBN 0-8493-1280-9. 
  • Brennen, Christopher (2005). Fundamentals of Multiphase Flow. Cambridge University Press. ISBN 0-521-84804-0.