Preparing the Simcenter STAR-CCM+ Simulation for Co-Simulation

Set up a Simcenter STAR-CCM+ simulation for co-simulation with GT-SUITE.

  1. Activate the following physics models on the relevant fluid continuum:
    Group Physics Model
    Space Three Dimensional
    Time Implicit Unsteady, Explicit Unsteady, or PISO Unsteady
    Material Gas, Liquid, or Multi-Component Gas (Non-Reacting)
    Flow Coupled Flow or Segregated Flow
    Enabled Models Gradients (selected automatically)
    Equation of State Ideal Gas
    Energy any
    Viscous Regime any
    Optional Models Co-Simulation
    Co-Simulation Models GT-SUITE
    Optional Models Passive Scalar
    NoteThis model can be neglected if you represent all species of a multi-component gas with gas components.

    You can select further models from the Optional Models group to meet individual simulation requirements.

Simulation preprocessing in GT-SUITE generates a material database file, <GT-POWER_case_name>.chemkin_GT.dbs. To use the same material properties as GT-SUITE, import this file into Simcenter STAR-CCM+:
  1. Right-click the Tools > Material Databases node and select New Material Database.
  2. Right-click the new material database and select Import Properties.
  3. In the Open dialog, select the <GT-POWER_case_name>.chemkin_GT.dbs file and click OK.
  4. In the Import Properties dialog, select Import properties for all materials and click OK.
  5. In the Open dialog, select the <GT-POWER_case_name>.chemkin_GT.dbs file and click OK.
  6. In the Import Properties dialog, select Import properties for all materials and click OK.
When modeling multi-component gases, define a mixture component or passive scalar for each species defined in GT-SUITE. In general, use gas components to represent GT-SUITE species that have non-trace quantities, and passive scalars to represent GT-SUITE species that have trace quantities. A mixture component influences the physical properties of the simulation, thus providing the most accurate and realistic solution. A passive scalar has no effect on the physical properties of the simulation, which reduces processing times. If you use passive scalars for all species, specify a background fluid in the region.

To add a mixture component to the simulation:

  1. Expand the [physics continuum] > Models node.
  2. Right-click the Multi-Component Gas > Gas Components node and select Select Mixture Components...
  3. In the Select Mixture Components dialog, select gas components from the GT-POWER Materials database, then click Apply.
    Note Although the “fuel-combust” species is a liquid, you can represent it with a gas in the Multi-Component Gas model. This modeling approach does not affect results, as the gas only represents the species in Simcenter STAR-CCM+, with the physics values received from GT-SUITE.
To add a passive scalar to the simulation:
  1. Right-click the Passive Scalars node and select New.
To reduce the numerical round-off, set the reference pressure to the average pressure in GT-SUITE. You can identify the average pressure in GT-SUITE by running a standalone GT-SUITE analysis and using GT-POST to analyze the results.

To set the reference pressure:

  1. Select the [physics continuum] > Reference Values > Reference Pressure node and set the Value property.
    NoteAll pressures in Simcenter STAR-CCM+ are defined relative to the reference pressure. In GT-SUITE, all pressures are absolute. Take these differences into consideration when defining pressure values.
For best initialization, set the Simcenter STAR-CCM+ initial conditions to the average values from GT-SUITE, which you can obtain by running a standalone GT-SUITE analysis and using GT-POST to analyze the results:
  1. Expand the [physics continuum] > Initial Conditions node, and specify the initial conditions as follows:
    1. As the initial pressure in Simcenter STAR-CCM+ is relative to the reference pressure, set the Pressure value to the difference between the average pressure from GT-SUITE and the Simcenter STAR-CCM+ reference pressure.
    2. As the initial temperature in Simcenter STAR-CCM+ is an absolute value, set the Static Temperature value to be the same as the average temperature from GT-SUITE.
    3. When you model multi-component gases, set the species mass fractions to the average values from GT-SUITE, by setting the Species Mass Fraction value. Click (Custom Editor) to enter the mass fractions in an array.


Specify boundary types in the usual manner. The coupled boundary types determine the fields exchanged between GT-SUITE and Simcenter STAR-CCM+ during the co-simulation, as explained in Exchanged Fields.
  1. Specify the boundary types. For the boundary that couple with GT-SUITE, set the Type to either Mass Flow Inlet, Velocity Inlet, or Pressure Outlet.
    The recommended practice is to set the boundary type to mass flow inlet for all coupled boundaries—regardless of whether they are inlets or outlets. If you use a mass flow inlet, Simcenter STAR-CCM+ uses the boundary area, normal velocity, and density from GT-SUITE to determine the mass flow rate at the boundary. Small changes in density are reflected in the mass flow rate across the boundary.

    For coupled boundaries that have large negative flows (such as flows that are leaving the Simcenter STAR-CCM+ domain), use coupled velocity inlet boundaries. Using coupled mass flow inlet boundaries can sometimes lead to instabilities for some models. If you use a velocity inlet, Simcenter STAR-CCM+ takes the normal velocity from GT-SUITE and applies it uniformly at the coupled boundaries.

    Note Setting all the Simcenter STAR-CCM+ coupled boundaries to mass flow or velocity inlets does not have the same negative numerical repercussions that would occur in a standalone CFD model. The absolute pressure of the CFD model drives the GT-SUITE solution and sets the mass flux or velocity at the boundary.
  2. Specify boundary conditions in the usual manner. On the coupled boundaries, only specify turbulence settings, as all the other values are set by GT-SUITE.
  3. Complete the set up by specifying co-simulation settings, including the coupled boundaries, coupled species, and connection settings. For instructions, refer to the section, Specifying Co-Simulation Settings.