Specifying the Exchanged Fields

For each zone, specify the fields that are exported and imported during the co-simulation at the coupled parts selected for that zone. Simcenter STAR-CCM+ allows you to specify the exchanged fields using predefined mechanical and thermal fields, for common Fluid-Structure Interaction (FSI) and Conjugate Heat Transfer (CHT) applications, or auxiliary fields, for generic data exchange.

The predefined fields available for import and export depend on the simulation set up. Predefined mechanical fields, thermal fields, and auxiliary fields can coexist in the same co-simulation zone. For more information, see Exchanged Fields Reference.

In a typical FSI simulation, you model the response of a deformable solid to the mechanical forces exerted by a contacting fluid. In FSI co-simulation, the fluid simulation computes the fluid forces (pressure and wall shear stress), and the solid simulation computes the resulting solid displacements.

In CHT co-simulation, the fluid simulation computes the heat transfer coefficient and reference temperature, and the solid simulation computes the solid temperature.

For predefined FSI or CHT co-simulation:

  1. Set up the simulations as described in Preparing the Simulations for Co-Simulation.
  2. In each simulation, expand the relevant [Link] > Zones > [Zone] > Conditions node.
    The name of the zone in the fluid simulation must match the name of the corresponding zone in the solid simulation.
  3. In each coupled zone, right-click the Exported Fields node, select Add Mechanical Field (for FSI) or Add Thermal Field (for CHT) and choose:
    Simulation FSI CHT
    Fluid Simulation either Pressure, Wall Shear Stress, or both. Heat Transfer Coefficient and Reference Temperature
    Solid Simulation Displacement Temperature
  4. In CHT simulations, select the Exported Fields > Heat Transfer Coefficient and the Reference Temperature nodes in turn and set the Heat Transfer Coefficient and Reference Temperature properties using consistent field functions:
    Heat Transfer Coefficient Field Function Reference Temperature Field Function
    Local Heat Transfer Coefficient Local Heat Transfer Reference Temperature
    Specified Y+ Heat Transfer Coefficient Specified Y+ Heat Transfer Reference Temperature
  5. Similarly, in each coupled zone right-click the Imported Fields node, select Add Mechanical Field (for FSI) or Add Thermal Field (for CHT) and choose the relevant fields in each simulations. The fields that are imported by one simulation must match the fields that are exported by the other simulation.
The heat transfer coefficient and reference temperature computed in the fluid simulation can be applied to the coupled solid boundaries as convective fluxes or environmental fluxes (see Thermal Specification). To set the thermal specification:
  1. In the solid simulation, select the relevant [Zone] > Conditions > Thermal Specification Management node and set Option to either Convection or Environment, as required.

In each simulation, Simcenter STAR-CCM+ stores the imported data in field functions named Co-Simulation: [Imported Field Name] (for example, Co-Simulation: Imported Displacement).

To set boundary conditions automatically using these field field functions:

  1. Select the relevant [Zone] > Conditions > Imported Fields > [Imported Field] node and set Field Treatment to Managed.
    With this setting, Simcenter STAR-CCM+ automatically applies imported predefined fields to the coupled boundaries, setting the relevant boundary conditions (see Exchanged Fields Reference). Specifically:
    • If the morpher is active, Simcenter STAR-CCM+ uses the imported displacements to define the morphing motion of the coupled fluid boundary.

      Imported pressure and wall shear stress are applied to the coupled solid boundary as either a pressure profile (for pressure only import), or a traction profile (for import of wall shear stress, or pressure and wall shear stress).

    • Imported temperature, heat transfer coefficient, and reference temperature set the corresponding boundary values in the fluid and solid regions.
To export or import any other field functions that cannot be exchanged using predefined fields:
  1. In any simulation, right-click the Exported Fields or the Imported Fields node, as required.
  2. Select Add Auxiliary Field and choose between Scalar or Vector, as appropriate.
  3. Select the [Auxiliary Field] node and specify the field function to export/import.
  4. To use the imported auxiliary fields at the coupled boundaries, set the relevant boundary conditions manually using the field functions that store the imported data.
Simcenter STAR-CCM+ initializes the field functions associated with imported and exported fields as follows:
  • Imported field: Simcenter STAR-CCM+ initializes the field based on the initial conditions in the associated physics continuum. When initial conditions are not available, you manually initialize the imported field to a constant value.
  • Exported field: you manually initialize the imported field to a constant value.

To initialize a field manually:

  1. Select the relevant Exported Fields > [Exported Field] or Imported Fields > [Imported Field] node.
    When the field requires manual initialization, Simcenter STAR-CCM+ automatically sets the Initialization Method to User-defined Initialization Value. For cases where the field is initialized automatically, Simcenter STAR-CCM+ sets the Initialization Method to the appropriate option and no input is required.
  2. Select the relevant [Zone] > Values > Initialization Values > [Export: Field Name] or [Import: Field Name] node and specify the constant initialization value.

    For more information on all the properties available to imported and exported fields, see Exchanged Fields Reference.

To transfer data between the simulations, Simcenter STAR-CCM+ maps the specified fields between simulations across the coupled boundaries or regions. You control which fields are mapped by the current simulation, and which fields are mapped by the partner simulation, using the Mapping Option condition. See STAR-CCM+ Link Reference.

For each field mapped by the current simulation, Simcenter STAR-CCM+ adds a mapper control node under the relevant [Zone] > Values node. These mapper nodes reference data mappers that are defined within the Tools > Data Mappers node.

You can either create data mappers manually or rely on Simcenter STAR-CCM+ to create them automatically. If you do not create a data mapper for each of the mappers under the [Zone] > Values node, then one is created using default values when the co-simulation starts.

If the current simulation requires non-default control of the data mapping:

  1. Create a Data Mapper within the Tools > Data Mappers node and assign it to the corresponding mapper node under the [Zone] > Values node.
  2. For the data mapper, specify proximity constraints, normal direction constraints, interpolation method and any other settings. Simcenter STAR-CCM+ automatically sets part and field properties in both the source and target.
    Note You can inspect properties of a mapper you have created at any time, but you can inspect the properties of default mappers only after the co-simulation run has started.