33.3.17 Species Model Dialog Box

The Species Model dialog box allows you to set parameters related to the calculation of species transport and combustion. See Sections  15.1.2, 15.2.2, 15.3.1, 17.2, 18.2, and 19.2 for details about the items below.

Controls

Model   indicates which model, if any, is used to calculate species transport/combustion.

Off   disables species calculations.

Species Transport   enables the calculation of multi-species transport (either non-reacting or reacting, depending on the selection for Reactions). See Chapter  15 for details.

Non-Premixed Combustion   enables the calculation of turbulent reacting flow using the non-premixed combustion model. See Chapter  16 for details. This option is available only for turbulent flows using the pressure-based solver.

Premixed Combustion   enables the premixed turbulent combustion model. See Chapter  17 for details. This option is available only for turbulent flows using the pressure-based solver.

Partially Premixed Combustion   enables the partially premixed turbulent combustion model. See Chapter  18 for details. This option is available only for turbulent flows using the pressure-based solver.

Composition PDF Transport   enables the composition PDF transport model. See Chapter  19 for details. This option is available only for turbulent flows using the pressure-based solver.

Reactions   contains options related to the modeling of reacting flow. (This section of the dialog box appears only when Species Transport or Composition PDF Transport is the specified Model.)

Volumetric   enables the calculation of reacting flow using the finite-rate formulation. See Section  15.1 for details.

Wall Surface   enables the calculation of wall surface reactions. See Section  15.2 for details. This item will appear only if Volumetric is enabled.

Particle Surface   enables the calculation of particle surface reactions. See Section  15.3 for details. This item will appear only if Volumetric is enabled.

Integration Parameters...   is a command button that opens the Integration Parameters dialog box. This button appears for the species transport model, when Volumetric is enabled under Reactions and Stiff Chemistry Solver is enabled under Options or when Eddy-Dissipation Concept is enabled under Turbulence-Chemistry Interaction.

Wall Surface Reaction Options   contains additional options for wall surface reactions. This portion of the dialog box appears only if Wall Surface is enabled under Reactions.

Heat of Surface Reactions   (if enabled) includes the heat release due to surface reactions in the energy equation. You must remember to set appropriate formation enthalpies (standard state enthalpies) if you enable this option.

Mass Deposition Source   (if enabled) includes the effect of surface mass transfer in the continuity equation.

Aggressiveness Factor   is a numerical factor which controls the robustness and the convergence speed. This value ranges between 0 and 1, where 0 (the default) is the most robust, but results in the slowest convergence.

Options   contains additional options for the Species Transport model and for the Composition PDF Transport. (This section will not appear in the dialog box for the other models.)

Inlet Diffusion   includes the diffusion flux of species at inlet.

Diffusion Energy Source   (if enabled) includes the effect of enthalpy transport due to species diffusion in the energy equation.

Full Multicomponent Diffusion   enables the full multicomponent diffusion model. See Section  8.9.2 for details.

Thermal Diffusion   enables the thermal diffusion model. See Section  8.9.3 for details.

Stiff Chemistry Solver   enables the calculations for modeling stiff laminar flames. See Section  15.1.7 for details.

Liquid Micro-Mixing   is used to model liquid reactions. When the Liquid Micro-Mixing model is invoked, ANSYS FLUENT uses the volume-weighted-mixing-law formula to calculate the density.

KINetics From Reaction Design   enables the use of reaction rates-of-production from Reaction Design's KINetics module, coupled to ANSYS FLUENT's ISAT algorithm.

Include Temperature Fluctuations   enables the calculation of the multi-mode energy equation. This option is available when the composition PDF transport model is selected.

Mixture Properties   contains controls and information about the mixture being modeled. This section of the dialog box will not appear if Premixed Combustion is the selected under Model.

Mixture Material   contains a drop-down list of available mixture materials. When you first enable the Species Transport model, you can choose from all of the mixture materials defined in the database, or you can choose a "template'' and define your own material. (Click View... to open the Database Materials dialog box and check the properties of the mixture material selected in the list.) See Section  15.1.2 for details.

When you use the Non-Premixed Combustion or Partially Premixed Combustion model, this list will be inactive. The mixture material for a non-premixed or partially premixed combustion calculation will be determined from the content of the PDF file generated in ANSYS FLUENT using the PDF Options parameters.

Number of Volumetric Species   displays the number of gas-phase species in the selected Mixture Material. This is an informational display only; you cannot edit this value.

Number of Solid Species   displays the number of solid species defined in the selected Mixture Material. This is an informational display only; you cannot edit this value. (This list will appear only for Species Transport models involving Wall Surface reactions.)

Number of Site Species   displays the number of site species defined in the selected Mixture Material. This is an informational display only; you cannot edit this value. (This list will appear only for Species Transport models involving Wall Surface reactions.)

Turbulence-Chemistry Interaction   indicates which model is to be used for turbulence-chemistry interaction when the Species Transport model with Volumetric reactions is used.

Laminar Finite-Rate   computes only the Arrhenius rate (see this equation in the separate Theory Guide) and neglects turbulence-chemistry interaction.

Finite-Rate/Eddy-Dissipation   (for turbulent flows) computes both the Arrhenius rate and the mixing rate and uses the smaller of the two.

Eddy-Dissipation   (for turbulent flows) computes only the mixing rate (see this equation and this equation in the separate Theory Guide).

Eddy-Dissipation Concept   (for turbulent flows) models turbulence-chemistry interaction with detailed chemical mechanisms (see this equation and this equation in the separate Theory Guide).

Coal Calculator...   opens the Coal Calculator dialog box.

Options   contains parameters related to the Laminar Finite-Rate or the Eddy-Dissipation Concept model. This section of the dialog box will appear when Laminar Finite-Rate or the Eddy-Dissipation Concept is selected for Turbulence-Chemistry Interaction.

Flow Iterations Per Chemistry Update   specifies how often ANSYS FLUENT will update the chemistry during the calculation. Increasing the number can reduce the computational expense of the chemistry calculations.

Aggressiveness Factor   is a numerical factor which controls the robustness and the convergence speed. This value ranges between 0 and 1, where 0 (the default) is the most robust, but results in the slowest convergence.

Volume Fraction Constant   specifies the value of $C_{\xi}$ in this equation in the separate Theory Guide.

Time Scale Constant   specifies the value of $C_{\tau}$ in this equation in the separate Theory Guide.

PDF Options   contains options related for the non-premixed combustion model. (This section will appear only if Non-Premixed Combustion or Partially-Premixed Combustion is the selected Model.)

Inlet Diffusion   includes the diffusion flux of species at inlet.

Compressibility Effects   can be enabled to account for cases where substantial pressure changes occur in time and/or space when modeling a non-adiabatic system. See Section  16.2.2 for details.

Liquid Micro-Mixing   is used to model liquid reactions. When the Liquid Micro-Mixing model is invoked, ANSYS FLUENT uses the volume-weighted-mixing-law formula to calculate the density.

Chemistry   tab contains the parameters to define problems using the chemistry model. See Section  16.2 for details.

State Relation   

Equilibrium   enables the equilibrium chemistry model. See Section  16.2 for details.

Steady Flamelet   enables the steady laminar flamelet model. See this section in the separate Theory Guide for details.

Unsteady Flamelet   enables the Eulerian unsteady laminar flamelet model.

Diesel Unsteady Flamelet   enables the diesel unsteady laminar flamelet model. See Section  16.3.6 for details.

Energy Treatment   

Adiabatic   enables adiabatic modeling options for the problem.

Non-Adiabatic   enables nonadiabatic modeling options for the problem. See this section in the separate Theory Guide for details.

Coal Calculator   opens the Coal Calculator dialog box.

Stream Options   contains the parameters for the equilibrium chemistry model or the steady laminar flamelet model.

Secondary Stream   includes the secondary inlet stream in the model.

Empirical Fuel Stream   enables parameters to define fuel stream empirically. This option is available only with the full equilibrium chemistry model.

Empirical Secondary Stream   enables parameters to define secondary stream empirically. This option is available only with the full equilibrium chemistry model.

Model Settings   contains a list of parameter settings.

Operating Pressure   specifies the system operating pressure used to calculate the density using the ideal gas law. See Section  16.2.2 for details.

Fuel Stream Rich Flamability Limit   specifies the rich flammability limit for fuel stream when the equilibrium chemistry option is used. You will not set these if you have used the empirical definition option for fuel composition. See Section  16.2.5 for details.

Secondary Stream Flamability Limit   specifies the rich flammability limit for secondary stream when the equilibrium chemistry option is used. You will not set these if you have used the empirical definition option for fuel composition. See Section  16.2.5 for details.

Empirical Fuel Lower Calorific Value   specifies the lower calorific value of fuel stream.

Empirical Fuel Specific Heat   specifies the specific heat value of fuel stream.

Empirical Fuel Molecular Weight   specifies the molecular weight of the fuel stream.

Empirical Secondary Lower Calorific Value   specifies the lower calorific value of secondary stream.

Empirical Secondary Specific Heat   specifies the specific heat value of secondary stream.

Empirical Secondary Molecular Weight   specifies the molecular weight of the secondary stream.

Options   contains options related to the steady flamelet model.

Create Flamelet   enables the Import CHEMKIN Mechanism... button that opens the CHEMKIN Mechanism Import dialog box where you can import the CHEMKIN mechanism and thermodynamic data, to create a flamelet file. This option is available for the steady flamelet model. See Section  16.3 for details.

Import Flamelet   enables the Import Flamelet File... button that opens the Select File dialog box (see Section  2.1.6) where you can select the existing flamelet in ANSYS FLUENT. You can also set the file type parameters to import the existing flamelet in ANSYS FLUENT. See Section  16.3 for details. This option is available for the steady flamelet model.

File Type   contains the toggle buttons for two flamelet file types.

Standard   enables the import of an ASCII format standard flamelet file.

Oppdif   enables the import of a binary format OPPDIF flamelet file.

CFX-RIF   enables the import of an ASCII format CFX-RIF flamelet file.

Mixture Fraction Method   contains the three methods of computing the mixture fraction profile along the laminar flamelet.

Drake   calculates the mixture fraction using carbon and hydrogen elements.

Bilger   calculates the mixture fraction using hydrocarbon formula.

Nitrogen   calculates the mixture fraction in terms of nitrogen species.

Oppdif Flamelet Type   gives you have a choice of importing Single or Multiple OPPDIF files.

Import Flamelet File for Restart...   opens the Select File dialog box (see Section  2.1.6) in which you can save the existing flamelet in ANSYS FLUENT to use when running an existing case.

Thermodynamic Database File Name   specifies a path for the thermodynamic database file to be read.

Boundary   tab contains the list of boundary species and related parameters. This is available only for equilibrium chemistry model. See Section  16.4 for details.

Species   contains the list of the species used in the problem..

Fuel   specifies the fuel species.

Oxid   specifies the oxidizing species.

Second   specifies the secondary species.

Boundary Species   allows to specify the species you want to add or remove from the model. You can type the species chemical formula in the text box below it.

Add   adds the species in the model.

Remove   removes the species from the model.

List Available Species   prints a list of all species in the thermodynamic database file (thermo.db) in the console window.

Temperature   specifies the temperature of different streams that you have defined.

Fuel   is the temperature of the fuel inlet in the model.

Oxid   is the temperature of the oxidizer inlet in the model.

Second   is the temperature of the secondary stream inlet in the model.

Specify Species in   allows to define the unit of species concentration.

Mass Fraction   allows to specify the species in terms of mass fraction.

Mole Fraction   allows to specify the species in terms of mole fraction.

Control   tab contains the parameters for exclusion and inclusion of equilibrium species. This is available only for equilibrium chemistry model. See Section  16.5.1 for details.

Species Excluded from Equilibrium   lists the species excluded from equilibrium calculation.

Species Zeroed in Initial Unsteady Flamelet   lists the slow-forming species that are zeroed in the initial flamelet profile.

Add   allows to add equilibrium species.

Remove   allows to remove equilibrium species.

List Available Species   prints a list of all species in the thermodynamic database file in the console window.

Flamelet Controls   allows you to adjust the controls for the flamelet solution. Note that the Create Flamelet option in the Chemistry tab must be selected for the Steady Flamelet model for these controls to be available.

Initial Fourier Number   sets the first time step for the solution.

Fourier Number Multiplier   increases the time step at subsequent times. Every time step after the first is multiplied by this value.

Relative Error Tolerance and Absolute Error Tolerance   specifies the local error controls during numerical integration.

Flamelet Convergence Tolerance   specifies the maximum absolute change in species fraction or temperature at any discrete mixture-fraction.

Maximum Integration Time   specifies the maximum total elapsed time for flamelet calculation. ANSYS FLUENT will stop the flamelet calculation after the total elapsed time has exceeded this value.

Flamelet   tab allows you to adjust the controls for the flamelet solution. See Section  16.5.2 for details.

Flamelet Parameters   consist of the controls for the flamelet solution.

Number of Grid Points in Flamelet   specifies the number of mixture fraction grid points distributed between the oxidizer ( $f=0$) and the fuel ( $f=1$).

Maximum Number of Flamelets   specifies the maximum number of laminar flamelet profiles to be calculated.

Initial Scalar Dissipation   is the scalar dissipation of the first flamelet in the library.

Scalar Dissipation Step   specifies the interval between scalar dissipation values (in s $^{-1}$) for which multiple flamelets will be calculated.

Unsteady Flamelet Parameters   consist of the controls for the unsteady flamelet solution.

Number of Grid Points in Flamelet   specifies the number of mixture fraction grid points distributed between the oxidizer ( $f=0$) and the fuel ( $f=1$).

Mixture Fraction Lower Limit for Initial Probability   is the limit at which the unsteady flamelet model temporally convects and diffuses a marker probability equation through a steady-state ANSYS FLUENT flow-field.

Maximum Scalar Dissipation   is where flamelets extinguish at large scalar dissipation (mixing) rates.

Courant Number   is the number at which ANSYS FLUENT automatically selects the time step for the probability equation based on this convective Courant number.

Calculate Flamelets   begins the laminar flamelet calculation.

Display Flamelets...   opens the Flamelet 3D Surfaces dialog box (see Section  16.6.4) from which you can display 2D plots and 3D surfaces showing the variation of species fraction or temperature with the mean mixture fraction or scalar dissipation.

Initialize Unsteady Flamelet Probability   initializes the unsteady flamelet and its probability marker equation.

Display Unsteady Flamelet...   opens the Flamelet 2D Curves dialog box from which you can display 2D plots of the different variables.

Table   tab contains parameters to create the look-up table. See Section  16.7 for details of the items listed below.

Table Parameters   consist of the controls for the lookup table.

Number of Mean Mixture Fraction Points   is the number of discrete values of $\overline{f}$ at which the look-up tables will be computed.

Number of Secondary Mixture Fraction Points   is the number of discrete values of $p_{\rm sec}$ at which the look-up tables will be computed. This option is available only when a secondary stream has been defined.

Number of Mixture Fraction Variance Points   is the number of discrete values of $\overline{f^{'2}}$ at which the look-up tables will be computed. This option is available only when no secondary stream has been defined.

Maximum Number of Species   is the maximum number of species that will be included in the look-up tables.

Number of Mean Enthalpy Points   is the number of discrete values of enthalpy at which the three-dimensional look-up tables will be computed. This input is required only if you are modeling a non-adiabatic system.

Minimum Temperature   is used to determine the lowest temperature for which the look-up tables are generated (see this figure in the separate Theory Guide). This option is available only if you are modeling a non-adiabatic system.

Include Equilibrium Flamelet   specifies that an equilibrium flamelet (i.e., $\chi=0$) will be generated in ANSYS FLUENT and appended to the flamelet library before the PDF table is calculated. This option is available only when you are generating more than one laminar flamelet.

Calculate PDF Table   generates the look-up table.

Display PDF Table   opens the PDF Table dialog box where you can display 2D plots and 3D surfaces showing the variation of species mole fraction, density, or temperature with the mean mixture fraction, mixture fraction variance, or enthalpy.

Premixed   tab contains parameters needed to modify the piecewise-linear points. See Section  18.2.2 for the details.

Partially Premixed Mixture Properties   contains the list of properties that you can modify. Edit... opens the Quadratic Mixture Fraction dialog box where you can modify the values of the polynomial coefficients.

For each polynomial function of $\overline{f}$ under Partially Premixed Mixture Properties you can click Edit... and specify values for Coefficient 1, Coefficient 2, Coefficient 3, and Coefficient 4 in the appropriate Quadratic of Mixture Fraction dialog box.

Premixed Combustion Model Options   contains options for the premixed combustion model. (This section will appear only if Premixed Combustion is the selected Model.)

Adiabatic   enables the adiabatic premixed combustion model, which calculates temperature using this equation in the separate Theory Guide.

Non-Adiabatic   enables the non-adiabatic premixed combustion model, which calculates temperature using this equation in the separate Theory Guide.

Flame Speed Model   contains options for choosing a flame speed model.

Zimont Turbulent Flame Closure   allows you to choose the Zimont turbulent flame closure model.

Extended Coherent Flamelet Model   allows you to choose the Extended Coherent Flamelet model.

Zimont Model Constants   contains model constants for the Zimont premixed combustion model. (This section will appear only if Premixed Combustion or Partially Premixed Combustion is the selected Model and if the Zimont Turbulent Flame Closure flame speed model is chosen.)

Turbulent Length Scale Constant   specifies the value of $C_D$ in this equation in the separate Theory Guide.

Turbulent Flame Speed Constant   specifies the value of $A$ in this equation in the separate Theory Guide.

Stretch Factor Coefficient   specifies the value of $\mu_{\rm str}$ in this equation in the separate Theory Guide.

Turbulent Schmidt Number   specifies the value of ${\rm Sc}_t$ in this equation in the separate Theory Guide.

Wall Damping Coefficient   specifies the value of $\alpha_w$ in this equation .

Extended Coherent Flamelet Model Constants   contains model constants for the Extended Coherent Flame Model. (This section will appear only if Premixed Combustion or Partially Premixed Combustion is the selected Model and if the Extended Coherent Flame Model flame speed model is chosen.) See Section  17.4.1 for details.

ITNFS Treatment   contains a drop-down list of the available ITNFS treatments: constant-delta, meneveau, blint, poinsot, and constant.

ITNFS Flame Thickness   sets the flame thickness ( this equation in the separate Theory Guide).

Turbulent Schmidt Number   set the turbulent Schmidt number (Sc $_t$).

Wall Flux Coefficient   set the wall flux coefficient.

PDF Transport Options   contains options for the Composition PDF Transport combustion model. (This section will appear only if Composition PDF Transport is the selected Model.)

Lagrangian   solves the composition PDF transport equation by stochastically tracking Lagrangian particles through the domain.

Eulerian   assumes a shape for the PDF, allowing Eulerian transport equations to be derived.

Mixing   tab contains the mixing models.

Mixing Model   contains options to specify the method for modeling molecular diffusion. (This section will appear only if Composition PDF Transport is the selected Model.) See this section in the separate Theory Guide for details.

Modified Curl   enables the modified curl model for molecular diffusion.

IEM   enables the IEM model for molecular diffusion.

EMST   enables the EMST mixing model for molecular diffusion.

Mixing Constant   specifies the value of the mixing constant $C_{\phi}$ in this equation and this equation in the separate Theory Guide.

Boundary   tab allows you to define the fuel and oxidizer compositions. This is only available if you select Eulerian as the PDF Transport Option.

Species   consists of the fuel species and the oxidizer.

Fuel   is the mole or mass fraction of the fuel stream. The sum of mass or mole fractions of all species in the fuel stream should be 1.

Oxidizer   is the mole or mass fraction of the oxidizer stream. The sum of mass or mole fractions of all species in the fuel oxidizer stream should be 1.

Specify Species in   specifies the species as a Mass Fraction or Mole Fraction.

Control   tab contains Lagrangian PDF transport parameters.

PDF Transport Parameters   allows you to set the Particles Per Cell.

Particles Per Cell   sets the number of PDF particles per cell. Higher values of this parameter will reduce statistical error, but increase computational time.

Local Time Stepping   toggles the calculation of local time steps. If this option is disabled, then you will need to specify the Time Step directly (see this equation in the separate Theory Guide). This option is available for steady-state simulations.

Convection #   specifies the particle convection number (see $\Delta t_{\rm conv}$ in this equation in the separate Theory Guide).

Diffusion #   specifies the particle diffusion number (see $\Delta t_{\rm diff}$ in this equation in the separate Theory Guide).

Mixing #   specifies the particle mixing number (see $\Delta t_{\rm mix}$ in this equation in the separate Theory Guide).