FGM Table Reference

The Flamelet Generated Manifold (FGM) model uses the table that is generated by the FGM Table Generator.

FGM Table Generator

Properties

None

Right-Click Actions

Import Table…

Imports a previously saved FGM table.

注	Since tables are saved in single precision, Table Precision—under the FGM Table Generator > Parameters node—is switched to Single after importing a table.

Delete Table

Removes a stored table from memory. The flamelet table must be deleted before making changes to the table settings.

Stop Calculations

Stops the calculations during the flamelet library generation.

Child Nodes

The FGM Table Generator node contains the following sub-nodes:

Chemistry Definition
Fluid Streams (see Fluid Streams Reference)
Reactor Type
Parameters
FGM Table

Chemistry Definition

The Chemistry Definition describes the chemical reaction mechanism, which is the collection of all species in a reaction—reactants, intermediates, and products—and the corresponding set of all reactions. The Chemistry Definition also includes the thermodynamic properties, as well as, optionally, the transport properties. Including the transport properties file can increase accuracy for low Reynolds number flows where laminar mixture viscosity and thermal conductivity are comparable to their corresponding turbulent values, and also when tabulating laminar flame speeds where the simulation conditions are outside the range of the built-in correlations.

Properties

None

Right-Click Actions

Import Complex Chemistry Definition (Chemkin format): Activates a standard Open dialog that imports files for the complex chemistry definition in Chemkin™ format. Upon importing a chemistry definition, the reactions for the definition appear as sub-nodes of the Chemistry Definition node.; If you import transport data along with the chemical mechanism and thermal data, Simcenter STAR-CCM+ tabulates the molecular transport properties for the Dynamic Viscosity, Molecular Diffusivity, and Thermal Conductivity material properties. You can then choose to use these tabulated molecular transport properties after table generation, in the Multi-Component Gas node, by selecting the Flamelet Table option for each of the Material Properties.
Delete Complex Chemistry Definition: Removes the reactions and species in the chemistry definition.

Reactor Type

Option

0D Ignition: FGM tables are generated using a 0D Constant Pressure reactor. These flamelets are the fastest and most stable to generate, but typically tend to over-predict intermediate species such as OH and CO.; See 0D 点火反应器类型控制方程.
1D Premixed Strained: 1D opposed flow premixed flamelets are solved in progress variable space. This reactor type is the most appropriate for solving perfectly-premixed or partially-premixed turbulent flames.; See 1D 预混应变反应器类型控制方程.
1D Premixed Freely Propagating: 1D freely propagating premixed flamelets are solved in progress variable space.; This reactor type is the most appropriate for solving premixed flames when using the Turbulent Flame speed Closure (TFC) model or Coherent Flame Model (CFM) and the laminar flame speed is not accurately modeled by the Simcenter STAR-CCM+ laminar flame speed correlations, since the laminar flame speed is computed and tabulated during flamelet generation.; See Governing Equations for 1D Premixed Freely Propagating Reactor Type.

Parameters

Properties

Progress Variable Definition

Allows three ways to define the weights

W_{k}

of the un-normalized progress variable

y

as defined by Eqn. (3532). Ideally, the set of species weights results in the progress variable increasing monotonically from unburnt to burnt.

Species Weights: Adds a Species Weights sub-node which allows you to define the individual progress variable species weights $W_{k}$ manually. You select species that correspond to the typical products of the combustion reaction.
Chemical Enthalpy: The progress variable species weights, $W_{k}$ are set to the chemical formation enthalpies ( $h$ ) of each species. Values for $h_{k}$ are taken from the thermodynamic properties file which is imported as part of the reaction mechanism. See Reaction Mechanism Formats: Gas / Surface Thermodynamic Properties Files.
Optimal Weights: The optimal weights are calculated to minimize the gradients of the tabulated variables ( $ϕ$ ) with respect to the unnormalized progress variable $y$ , as well as ensuring that the progress variable increases monotonically through the flamelet. After optimization, the species weights are shown in the Species Weights sub-node.

Table Precision

Specifies the precision—Single or Double—to which the flamelet table is generated. The default is Single.

Child Nodes

Absolute Pressure

Value: The pressure that is used when generating the FGM table.

Species for Tabulation

Species: Allows you to select which species are stored in the flamelet table. These species are then made available in a simulation, for example, to use for post-processing in contours or reports.

Emissions

Thermal NOx

When activated, NOx source-term coefficients are calculated and tabulated.

Soot Moment

When activated, the soot moment model source-term coefficients are calculated and tabulated. Creates a Soot Moments Options sub-node which allows you to specify the Nucleation Option as either:

C2H2, see Eqn. (3682).
Single PAH Species (C16H10), see Eqn. (3679) and Eqn. (3680). The PAH precursor is recognised as any species which includes either A4 or A3R5 in the species name, or has the composition C16H10.

Numerical Settings

Defines the following properties, depending upon the option that is selected for Reactor Type. Also contains the Table Dimensions sub-node which you can use to set the dimensions for the flamelet table. See Table Dimensions Reference.


Properties	Reactor Type
Properties	0D Ignition	1D Premixed Freely Propagating	1D Premixed Strained
Minimum Temperature
Absolute ODE Tolerance
Relative ODE Tolerance
Flamelet Convergence Tolerance
Max Dissipation Rate

Minimum Temperature: Specifies the minimum temperature for enthalpy normalization in the flamelet table.
Absolute ODE Tolerance: Specifies the absolute tolerance of the ODE solver.
Relative ODE Tolerance: Specifies the relative tolerance of the ODE solver.
Flamelet Convergence Tolerance: The 1D premixed flamelet equations are integrated in time using the ODE solver Absolute Tolerance and Relative Tolerance until steady-state. Steady-state is determined when the average residual over all post-processing species and temperatures, and over all grid points, is less than the Flamelet Convergence Tolerance.
Max Dissipation Rate: The maximum dissipation rate of the normalized progress variable at stoichiometric conditions $χ_{Z, s t o}$ , that is used to determine the progress variable dissipation rate using Eqn. (3544) and Eqn. (3543). The default value of 1000 (s^-1) is approximately the scalar dissipation rate of a freely propagating flame.
Analytical Jacobian: When activated, an analytical Jacobian is used in the ODE solver instead of the numerical Jacobian.

Species Weights

The following values for the progress variable species weights,

W_{k}

in Eqn. (3532), are set by default. However, these values can be edited manually prior to generating the table.

If CO and CO2 are present in the mechanism, they are both set to 1.0 and all other species weights are set to 0.0.
If neither CO or CO2 are present in the mechanism, but H2 and H2O are present (for example, during hydrogen combustion), H2O is set to 1.0 and all other species weights are set to 0.0.

Heat Loss Ratio Range

Specifies the heat loss ratio range. You can increase the enthalpy space that is covered in the Flamelet table in response to heat loss ratio warnings, or decrease it for better resolution. For example, if your simulation involves 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.

You can set either the minimum heat loss ratio limit or the maximum heat loss ratio limit to 0, but you cannot have both set to 0 at the same time.

Minimum Heat Loss Ratio: Sets the minimum heat loss ratio limit.
Maximum Heat Loss Ratio: Sets the maximum heat loss ratio limit. However, if the resulting minimum temperature drops below a physical limit, the temperature is clipped to the table minimum temperature that is specified at the table generation.

After a table is generated, these values cannot be changed unless the table is deleted first.

FGM Table

The FGM Table node has the following options available from the context menu:

Properties

Save Table in .sim File

When activated, stores the flamelet table in the sim file. When deactivated, the flamelet table is not stored in the .sim file—which is useful to save disk space when using the same flamelet table in different .sim files, or when auto-saving many sim files. If the flamelet table is required for future use, you must export it manually by right-clicking the flamelet table node and selecting Export Table. Then save it separately from the .sim file.

Path for Table Read

Specifies the file path location of the flamelet table file that has been exported from Simcenter STAR-CCM+ and saved previously. Useful to reduce the .sim file size and save disk space when several .sim files use the same flamelet table.

Verbosity

When activated, if selected tolerance criteria are not met in adaptive grid generation steps, Simcenter STAR-CCM+ prints a summary of tolerance warnings to the Output window at each step during the table generation.

For example:

WARNING: For 'Heat Loss Ratio' the   maximum error of 0.00652988 is greater than the specified tolerance of 0.0001. To achieve the prescribed tolerance, delete the table, increase the maximum number of points (currently 9) and regenerate the table.

When deactivated, all of the warning messages about exceeding the defined tolerance for adaptive table dimensions are hidden.

Right-Click Actions

Generate FGM Library and Construct Table: Generates the FGM library and constructs the FGM table (performs PDF integrations) in Simcenter STAR-CCM+ using the properties and table dimensions that are specified under the FGM table node. The progress is displayed in the Output window.
Import FGM User Library File and Construct Table...: Imports the FGM user library file and constructs the FGM table (performs PDF integrations) in Simcenter STAR-CCM+ using the properties and table dimensions that are specified under the FGM table node. The progress is displayed in the Output window. See Loading Library Tables.
Print Estimated Maximum Table Size: Prints the estimated maximum table size (in KB) in the output window. This value also appears as a read-only property of the Table Dimensions node.
Export Table: Saves the FGM table that is stored in the memory of Simcenter STAR-CCM+ to a file with extension .tbl.
Delete Table: Removes a stored table from memory. The flamelet table must be deleted before making changes to the table settings.
Stop Calculations: Stops the calculations during the flamelet library generation.
Print Table Summary: The Output window displays a summary of the table parameters and conditions with which the table was built. When running the simulation, if the current parameters and conditions differ from those that were specified when the table was built, a warning is displayed in the Output window at each iteration.; Parameters and conditions 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.

Child Nodes

Final Table Grid Size: Contains sub-nodes for each of the table dimensions. Each table dimensions sub-node displays the (read only) Number of Grid Points that are used from the data for that parameter. The values are specified before building the table by defining settings under the Table Dimensions node. See Table Dimensions Reference.
FGM XY Plots: To visualize the flamelet generated manifold flamelet table, you can create an XY plot. Right-click this node and select New Plot. See Flamelet Table XY Plots Reference.