Defining Initial Fluid Fractions for a VOF Method Analysis

You can define the initial fraction of the two fluids in a volume of fluid (VOF) method analysis.

Before you begin: You must have your spatially mapped data prepared if you want a material distribution that varies in space. The mapped data should specify different fluid fraction values at various points in space.
Note: Because the VOF method assumes that the fluids are immiscible, you should specify initial fluid fractions of 1 for the reference material and 0 for the secondary material. The app does not perform this validation.
See Also
About Initial Mass Fractions in Multispecies Flow Simulations
In Other Guides
Defining a Fluid Domain
Editing Simulation Features
Support Selection
  1. From the Initial Conditions section of the action bar, click Initial Fluid Fractions .
  2. Optional: Customize the default Name for the initial fluid fractions definition.
  3. If gravitational effects are enabled in the fluid physics (see About Gravity in a Flow Simulation), you can define a material distribution other than the standard fluid fraction. Choose one of the following options from the Material Distribution list:
    OptionDescription
    Volume Fraction Defines a standard fluid fraction.
    Elevation Defines a free-surface elevation that initializes the flow with a material distribution consisting of a flat free-surface, in which the reference material is located below the specified elevation and the secondary material above. The app defines the elevation with respect to the global axis and in the direction of the gravity. The free-surface is normal to gravity.
  4. If the material distribution is uniform in space:
    1. From the distribution options, select Uniform value.
    2. Enter a value of either 0 or 1 for the type of material.
  5. If the fluid material distribution vary according to spatially mapped data, do the following:
    1. Select Mapped spatial data from the distribution options.
    2. Click Table.
      The Field Distribution dialog box opens.
    3. Choose the Data source for the mapped fluid fraction values:

      • Table: Enter or import the mapped data into the table.

      • Referenced document: Select a 3DEXPERIENCE document that contains the mapping data. Click to search for the document in the 3DEXPERIENCE platform database. For details about the file format required, see Mapping Data File Formats.

        Changes in the referenced document are taken into account every time the simulation is run.

    4. If Data source is set to Table, specify the mapped data in the table:

      • To import the data, right-click anywhere in the table and select Import. For details about the file format required, see Mapping Data File Formats.
      • To enter the data manually, double-click in each cell and enter a value. For example, enter x-, y-, z-coordinates and the corresponding fluid fraction Value in each row of the table.

    5. Enter the Value outside the mapped region. This is a default fluid fraction value.

      The simulation attempts to map all of the source data points and their associated fluid fraction values onto points in the target model. For any target points where the simulation cannot map to a source point, the app substitutes this user-defined value.

    6. Select an Axis system definition for the coordinates of the mapped data values.

      • Global: Aligns the local feature triad with the global coordinate system.

      • Local: Aligns the local feature triad with a selected axis system in the model.

        Using a custom local axis system simplifies the three-dimensional definition of points in space—the x-, y-, z-coordinates are interpreted in the context of the local coordinate system.

    7. Select Plot Data to display symbols that indicate the locations and magnitudes of the mapped values on the model.

      Tip: If you click any row in the data table, the corresponding source point is highlighted on the model.

    8. To adjust the search control parameters, expand the Search tolerance.

      See Mapping Search Controls and Mapping Search Control Options for descriptions of these parameters.

    9. To complete the spatial mapping data assignment, click OK.
  6. Click OK.