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23.9 Steps for Using a Multiphase Model

The procedure for setting up and solving a general multiphase problem is outlined below, and described in detail in the subsections that follow. Remember that only the steps that are pertinent to general multiphase calculations are shown here. For information about inputs related to other models that you are using in conjunction with the multiphase model, see the appropriate sections for those models.

See also Section  23.12.1 for guidelines on simplifying Eulerian multiphase simulations.

1.   Enable the multiphase model you want to use (VOF, mixture, or Eulerian) and specify the number of phases. For the VOF model, specify the VOF formulation as well.

Define $\rightarrow$ Models $\rightarrow$ Multiphase...

See Sections  23.9.1 and 23.10.1 for details.

2.   Copy the material representing each phase from the materials database.

Define $\rightarrow$ Materials...

If the material you want to use is not in the database, create a new material. See Section  8.1.2 for details about copying from the database and creating new materials. See Sections  23.10.5 and 23.11.3 for additional information about specifying material properties for a compressible phase (VOF and mixture models only). It is possible to turn off reactions in some materials by selecting none in the Reactions drop-down list under Properties in the Materials panel.

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If your model includes a particulate (granular) phase, you will need to create a new material for it in the fluid materials category ( not the solid materials category).

3.   Define the phases, and specify any interaction between them (e.g., surface tension if you are using the VOF model, slip velocity functions if you are using the mixture model, or drag functions if you are using the Eulerian model).

Define $\rightarrow$ Phases...

See Sections  23.9.3- 23.12.2 for details.

4.   (Eulerian model only) If the flow is turbulent, define the multiphase turbulence model.

Define $\rightarrow$ Models $\rightarrow$ Viscous...

See Section  23.12.3 for details.

5.   If body forces are present, turn on gravity and specify the gravitational acceleration.

Define $\rightarrow$ Operating Conditions...

See Section  23.9.4 for details.

6.   Specify the boundary conditions, including the secondary-phase volume fractions at flow boundaries and (if you are modeling wall adhesion in a VOF simulation) the contact angles at walls.

Define $\rightarrow$ Boundary Conditions...

See Section  23.9.8 for details.

7.   Set any model-specific solution parameters.

Solve $\rightarrow$ Controls $\rightarrow$ Solution...

See Sections  23.10.4 and 23.14 for details.

8.   Initialize the solution and set the initial volume fractions for the secondary phases.

Solve $\rightarrow$ Initialize $\rightarrow$ Patch...

See Section  23.14.1 for details.

9.   Calculate a solution and examine the results. Postprocessing and reporting of results is available for each phase that is selected.

See Sections  23.14 and 23.15 for details.

This section provides instructions and guidelines for using the VOF, mixture, and Eulerian multiphase models.




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