Reacting Channels Workflow

The Reacting Channel co-simulation model in Simcenter STAR-CCM+ allows you to exchange data between reacting channels that use a one-dimensional Plug Flow Reactor (PFR) and three-dimensional Simcenter STAR-CCM+ simulations.

Before setting up reacting channels, make sure that:
  • you have a fluid domain with a three-dimensional mesh that contains unmeshed voids that represent the reacting channels.
  • the Steady model is previously selected.
The steps in this workflow are intended to follow on from the initial steps in the Reacting Flow General Workflow.
NoteFor an example of how to use the Reacting Channel Co-Simulation model, see the Reacting Channels: Steam Methane Reforming tutorial. The tutorial demonstrates how you set up firebox and the physics for the reacting channels.

When using the reacting channel coupling model, set up at least one reacting channel co-simulation zone. Each reacting channel zone can represent several geometrical channels. At least two zones are required when simulating a reacting flow which exits channels in one zone (a Specified Inlet zone) and re-enters channels in another zone (a Re-Entry zone).



  1. For the physics continuum that represents the fluid domain that surrounds the reacting channels, select the following models—in addition to the models that are previously selected, with Auto-Select recommended models activated:
    Group Box Model
    Reacting Flow Models (when the Reacting model is selected)
    • Flamelet

      Often the most appropriate for firebox combustors.

    • Reacting Species Transport

      For detailed reaction mechanisms.

    Flamelet Models (when the Flamelet model is selected)

    Any

    For example, Flamelet Generated Manifold (FGM) is suitable for all premixed or partially premixed flames where the flamelet assumption is valid.

    Further model selections are necessary.

    Reacting Species Models (when the Reacting Species Transport model is selected)

    Any

    For example, Complex Chemistry is applicable for combustors with multiple fuel streams, and with kinetically dominant processes such as flame quenching.

    Further model selections are necessary.

    Optional Models Co-Simulation
    Co-Simulation Models Reacting Channel
    Reacting Channel Coupling Models Reacting Channel Steady Coupling (selected automatically)
  2. Click Close.
    Simcenter STAR-CCM+ adds the External Links node and a single Reacting Channel Co-Simulation sub-node.
Within one simulation, it is possible to create more than one reacting channel co-simulation. Separate reacting channel co-simulations are necessary if more than one chemical mechanism is required in the simulation. Each reacting channel co-simulation must contain at least one reacting channel zone. You can specify reaction conditions and values for each reacting channel co-simulation and also define further conditions and values that are specific to each reacting channel zone.
  1. Create a Reacting Channel Co-Simulation node for each reacting channel mechanism that you want to use. To specify more than one reacting channel mechanism, right-click the External Links node and select New > Reacting Channel Link.
    A Link node appears, which you can set up as another reacting channel co-simulation.
Specify the Conditions and Values for each Reacting Channel Co-Simulation.
  1. Select the Reacting Channel Co-Simulation > Values > Coupling Strategy node and specify the parameters that are required for coupling.
  2. Right-click the Reacting Channel Co-Simulation > Values > Chemistry Definition node and select Import Chemistry Definition (Chemkin format).
  3. In the Import Chemkin Files dialog, browse to and select the appropriate files, then click OK. When you intend to use user coding, you select an edited Chemkin file for the Fluid Chemistry Reaction File which contains a list of atoms and species only.
  4. Select the Reacting Channel Co-Simulation > Values > Chemistry Definition > Reacting System Properties > Species Reaction Sources node and set Method to either:
    • To use internally-defined reaction types in the standard Chemkin format, select Internal (default).
    • To specify reactions with user coding, select User-Defined.
  5. To import and set up the user coding:
    1. Right-click the Tools > User Code node and select New User Library.
    2. In the Open dialog, browse to and select the appropriate library, then click Open.
    3. Select the Species Reaction Sources > User-Defined node and set User Function to [user_function].
    4. Select the Reacting System Properties > User-Defined Species Sources Specification node and set Method to one of the following:
      • To calculate the species sources from the user code, select Calculate Species Sources. Then select the User-Defined Species Sources Specification > Calculate Species Sources node and make sure that Internal Reaction Energy Source is activated.
      • To modify the species sources from the internally-defined chemistry, select Modify Internal Species Sources.
The Zones node contains a Zone 1 node by default. If you are simulating re-entry from one set of reacting channels to another, you must set up at least two zones.
  1. To create more reacting channel zones, right-click the Reacting Channel Co-Simulation > Zones node and select New.
    A Zone [2] node appears.
  2. To specify the boundaries for a reacting channel zone, group the boundaries for each reacting channel zone.
    1. Right-click the Regions > [Region] > Boundaries node and select New Group.
    2. Rename the New Group node appropriately.
    3. Expand the Boundaries node and multi-select the boundaries for one reacting channel zone.
    4. Drag the selected boundaries on to the [New Group] node.
    You can use the [New Group] node to edit the Properties, Conditions, and Values of all boundaries that it contains.
Each zone represents one reacting channel (a group of geometrical channels) and contains a set of conditions and values which are applied to the boundaries that you specify for that reacting channel zone.
  1. Right-click the [New Group] node and select Edit.
  2. In the Multiple Objects dialog, expand the Physics Conditions > External Code Coupling Specification node and set External Code Coupling Specification to the Reacting Channel Co-Simulation Zone for the selected boundaries.
  3. Group the remaining boundaries as necessary, and select an appropriate zone for the External Code Coupling Specification for each group of boundaries.
  4. Specify the Conditions and Values for each Zone within each Reacting Channel Co-Simulation.


    In particular, specify the following conditions and values:

    1. Conditions > Reacting Channel Inlet Type, Inlet Type:
      • To simulate uninterrupted flow into this zone from another zone, select Re-Entry. When you select Re-Entry for one zone, make sure that at least one other zone is set to Specified Inlet. The conditions and values that are not available to set for the Re-Entry zone are taken from the Specified Inlet zone.
      • To simulate flow between the inlet and outlet of reacting channels (from which you can, if required, specify the flow to re-enter reacting channels in a zone that is set as Re-Entry), select Specified Inlet.

      The diagrams below represent two possible scenarios. In the first diagram, the channel on the left must be in a zone that is set to Specified Inlet. The remaining channels are then grouped into zones with the same properties—one re-entry zone in which the flow orientation is downwards, and one re-entry zone in which the flow orientation is upwards.



      It is also possible to simulate multiple channels in a Specified Inlet zone—as long as these channels are all receiving an external flow that is not from a re-entry channel.



    2. Conditions > Reacting Channel Type, Correlation Type:
      • To simulate reacting channels that are void of any porous material, through which the reacting material will flow freely, select Pipe.
      • To simulate reacting channels that are packed with porous material through which the reacting material will pass through, select Packed Bed. You can specify the parameters of the porous material.


    3. Conditions > Heat Transfer Coefficient Correlation, Correlation Type.
    4. If the Inlet Type is set to Re-Entry, expand the Values > Re-Entry Boundaries node and specify the Outlet Boundary from which each [re-entry boundary] receives the flow.
    5. Values > Wall Orientation, Orientation.
      Make sure that the direction of flow in each zone is correct.
    6. Set other [Zone] > Conditions and [Zone] > Values as necessary.
  5. Set the parameters of any other [Continuum] > Models, as required.
  6. For the continuum that represents the fluid domain which surrounds the reacting channels, define any necessary parameters for the Reference Values and Initial Conditons.
    Make sure that you specify the initial Species Mass Fraction.
  7. Define any necessary Physics Conditions and Values for the Region and Boundaries.
    • For the inlet boundaries, specify the Species Mass Fraction and the Mass Flow Rate.
    • For the wall boundaries within the reacting flow region, specify the Surface Emissivity.
  8. Return to the Reacting Flow General Workflow.