Multiphase flow modeling involves the simultaneous flow of mixtures of different phases, such as gases in liquids or liquids in gases. There are two main approaches to numerically model multiphase flows in ANSYS Fluent: the Euler-Lagrange approach and the Euler-Euler approach. The Discrete Phase Model (DPM) is a multiphase model that tracks the dispersed phase in a Lagrangian reference frame, with the continuous phase modeled using Eulerian methods and the two phases coupled through source terms.

1. Multiphase flow modeling

2.  What is a multiphase flow ?
• Multiphase flow is a phenomena of simultaneous flow of
mixtures of phases such as gases (like bubbles ) in liquid , or
liquid (like droplets) in gases and similar such flows.
• By multiphase flow we mean that its a mixture of phase and
each phase in it has a distinct velocity field.
• Multi-phase flows exist in many different forms.
• Two-phase flows can be classified according to the state of
the different phases :
- Gas-Liquid mixture
- gas-solid mixture
- Immiscible-liquid mixture
- Liquid-solid mixture

3.  Multiphase Modeling by Ansys fluent :
 There are tow approaches for the numerical calculation of multiphas
1. The Euler – Lagrange approach :
The Lagrangian discrete phase model in FLUENT follows the Euler-
Lagrange approach .
2 . The Euler-Euler approach :
In FLUENT, three different Euler-Euler multiphase models are
available: the volume of fluid (VOF) model, the mixture model,
and the Eulerian model .

4.  Discrete Phase Model (DPM) :
• Discrete Phase Model is a multiphase model in which the
dispersed phase is tracked in a lagrangian reference frame .
• Two different phases are defined in the DPM model:
A continuous phase and a particle phase .
• The discrete phase is modeled by the lagrangian method .
• The continuous phase is modeled by eulerian method
• The discrete and the continuous phases are coupled through
sources terms in the governing equations .

5.  Coupling between phases :
• One-way coupling :
• DPM source term is updated .
• Source term of continuous phase is not updated
- Particle motion is affected by the continuous phase .
- Continuous phase is not affected by the particle flow .
• Two-way coupling :
• Transfer of momentum, energy and mass from particles
to the continuous phase is considered by means of source
terms.
• Source terms of both DPM and continuous phase are
updated .
- Particles and continuous flow interact with each other .

6.  Discrete Phase Modeling Setup :
• Type of injection .
• Initial conditions .
• Turbulence
Models .
• Heat and mass
transfer laws .
• Physical Modeling
inputs .
• Tracking parameters .
• Numerics .
• Interaction with
continuous phase .
• Particle behavior at
boundaries .

7.  DPM Calculation - Steady Flow :

8.  DPM Calculation - Unsteady Flow :