Creating Flamelet Tables

You can import the chemistry definition in standard Chemkin format—using ASCII files and then have Simcenter STAR-CCM+ generate the flamelet tables directly.

You can find the [flamelet model] Table Generator node within physics continua (or phases) that use a flamelet model.

To speed up the flamelet table generation, you can generate flamelet tables in Simcenter STAR-CCM+ when using multiple processors in parallel.

Import the chemistry definition that is used to create a flamelet table in Simcenter STAR-CCM+.
1. Right-click the [physics continuum] / [phase] > [flamelet model] Table Generator > Chemistry Definition node and select Import Complex Chemistry Definition (Chemkin format).
2. Select appropriate files for each of the required fields.
  - Chemical Mechanism File: Contains the chemistry of the reactions.
  - Thermodynamic Properties File: Contains details of the thermal properties.
  - Import Transport Properties File: Activates the import of the Transport Properties File. Importing this file is optional.
  - Transport Properties File: If Import Transport Properties File is activated, select a file which contains details of the species transport properties. If you select a transport properties file here, under the Multi-Component Gas > Material Properties node, the Dynamic Viscosity, Thermal Conductivity, and Molecular Diffusivity nodes then contain the option to set the Method to Flamelet Table. Simcenter STAR-CCM+ calculates the mean molecular dynamic viscosity and thermal conductivity from the flamelet species and temperature, and molecular diffusivity from the unity Lewis number assumption Eqn. (138).
  See Reaction Mechanism Formats.
Specify the composition and temperature of the fluid streams for flamelet generation.
Make sure that the sum of the mass fractions or mole fractions for each stream equals 1.0.
1. Select the [flamelet model] Table Generator > Fluid Streams > Fuel node and specify the components of the fuel stream. If the fuel is premixed or partially-premixed with the oxidizer, include the correct proportions of fuel and oxidizer within this stream.
2. Select the [flamelet model] Table Generator > Fluid Streams > Oxidizer node and specify the components of the oxidizer stream. By default, the composition of the oxidizer stream is set to that of air.
See Fluid Streams Reference.
If you are creating an FGM flamelet table, select the [flamelet model] Table Generator > Reactor Type node and set one of the following options:
- 0D Ignition—is the default.
- 1D Premixed—is the most appropriate when modeling premixed combustion.
See Reactor Type.

Specify the table parameters under the [flamelet model] Table Generator > Parameters node.

Absolute Pressure	Set the table pressure.
Species for Tabulation	By default, the specified fuel and oxidizer species, as well as CO2 and H2O, are selected. However, make sure that you specify any more species that are to be included in the table. For example, you can add CO for monitoring emissions, or OH for monitoring the position of the flame front. When modeling NOx emissions, do not select any NOx species for tabulation.
Emissions	To model NOx and/or soot emissions, activate Thermal NOx and/or Soot Moments. NOx and/or soot source terms for the transport equation are tabulated during the generation of the table. Coefficients for NOx/soot are included in the final table and are transported as a passive scalar.
Numerical Settings	Default values are suitable in the majority of cases.
Species Weights	The default progress variable species weights are defined for CO and CO2—which is appropriate for the majority of hydrocarbon combustion simulations.
Heat Loss Ratio Range	Specify the range for the heat loss ratio. If heat loss ratio warnings appear, increase the enthalpy space that is covered in the flamelet table—or for better resolution, decrease it. For simulations that involve heat loss only, with no heat gain, you can set the minimum heat loss ratio limit to 0 and the maximum heat loss ratio to 1.0.

See,

When trying to reach a flamelet table grid independent solution, you can refine the grid resolution—for adaptive gridding tables you can decrease the tolerance, or for fixed tables you can increase the number of data points—then re-converge the solution until it stops changing.

If necessary, refine the flamelet table dimensions (grid resolution).
1. Expand the [flamelet model] Table Generator > [flamelet model] Table node.
2. Select each of the dimensions.
3. Adjust the Table Dimension property as required for each dimension node.
See Table Dimensions Reference.

When the flamelet table is set up, you generate the flamelet table.

Right-click the [flamelet model] Table Generator > [flamelet model] Table node and select Generate Library and Construct Table.
The time taken to generate the table varies depending on the number of dimensions and the level of refinement. The progress is described in the Output window.
注 If you run out of memory generating or importing large tables in parallel, use an MPI that supports the 3.1 standard, like Open MPI or Intel MPI.

You can create XY Plots to visualize the values that are stored in a flamelet table for each variable. You can use XY plots to make sure that the heat loss ratio covers the full range of temperatures that are required for certain mixture fractions.

To visualize values for variables that are stored in the flamelet table:

Right-click the [flamelet model] Table Generator > [flamelet model] Table > [flamelet model] XY Plots node, then select New Plot and the [variable] to plot.
Right-click the [flamelet model] XY Plots > [variable] node and select Add New Table View for Plotting.
In the Select Points for Plotting dialog, enter the parameters that are required for the table and click OK.
To display the XY plot, double-click the [flamelet model] XY Plots > [variable] node.

See Flamelet Table XY Plots Reference.

If required, you can also change the X-Axis Variable property to display different grid resolution variables.

For example, the following XY plot shows the thermal conductivity variable for the mixture fraction grid resolution variable:

注

Flamelet tables generally contain a large number of tabulated variables, including species and temperature. Cell values of a tabulated variable are not calculated until the variable is displayed in a plot or scene. Hence, when a new plot or scene is created, the variable is displayed as zero and only updated after an iteration.

If required, you can print a summary of the table conditions.

To print a summary of the table conditions that were used to generate the table, right-click the [flamelet model] Table node and select Print Table Summary.

The Output window displays a summary of the table parameters and conditions with which the table was built.

If a table exists, it is not possible to change a constant value for the table conditions in the GUI. However, table conditions can be changed, without deleting the table first, using global parameters instead of constant values for the conditions. See Global Parameters.

When executing the Print Table Summary action for tables that use global parameters, if the conditions differ from those that were specified when the table was built, a warning is displayed in the Output window at each iteration. These warnings are not displayed for tables that are imported from Simcenter STAR-CCM+ versions prior to 2406, or from tables that are constructed using DARS libraries.