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14.1.3 Enabling Species Transport and Reactions and Choosing the Mixture Material

The problem setup for species transport and volumetric reactions begins in the Species Model panel (Figure  14.1.1). For cases which involve multiphase species transport and reactions, refer to Section  23.8.

Define $\rightarrow$ Models $\rightarrow$ Species $\rightarrow$ Transport & Reaction...

Figure 14.1.1: The Species Model Panel
figure

1.   Under Model, select Species Transport.

2.   Under Reactions, turn on Volumetric.

3.   In the Mixture Material drop-down list under Mixture Properties, choose which mixture material you want to use in your problem. The drop-down list will include all of the mixtures that are currently defined in the database. To check the properties of a mixture material, select it and click the Edit... button. If the mixture you want to use is not in the list, choose the mixture-template material, and see Section  14.1.4 for details on setting your mixture's properties. If there is a mixture material listed that is similar to your desired mixture, you may choose that material and see Section  14.1.4 for details on modifying properties of an existing material.

When you choose the Mixture Material, the Number of Volumetric Species in the mixture will be displayed in the panel for your information.

figure   

Note that if you re-open the Species Model panel after species transport has already been enabled, only the mixture materials available in your case will appear in the list. You can add more mixture materials to your case by copying them from the database, as described in Section  8.1.2, or by creating a new mixture, as described in Sections  8.1.2 and 14.1.4.

As mentioned in Section  14.1.2, modeling parameters for the species transport and (if relevant) reactions will automatically be loaded from the database. If any information is missing, you will be informed of this after you click on OK in the Species Model panel. If you want to check or modify any properties of the mixture material, you will use the Materials panel, as described in Section  14.1.4.

4.   Choose the Turbulence-Chemistry Interaction model. Four models are available:

Laminar Finite-Rate   computes only the Arrhenius rate (see Equation  14.1-8) 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 Equations  14.1-26 and 14.1-27).

EDC   (for turbulent flows) models turbulence-chemistry interaction with detailed chemical mechanisms (see Equations  14.1-8 and 14.1-31).

5.   If you selected EDC, you have the option to modify the Volume Fraction Constant and the Time Scale Constant ( $C_{\xi}$ in Equation  14.1-29 and $C_{\tau}$ in Equation  14.1-30), although the default values are recommended. Further, to reduce the computational expense of the chemistry calculations, you can increase the number of Flow Iterations per Chemistry Update. By default, FLUENT will update the chemistry one per 10 flow iterations. For details about using the Integration Parameters... option, under Reactions, see Section  18.3.

6.   (optional) If you want to model full multicomponent diffusion or thermal diffusion, turn on the Full Multicomponent Diffusion or Thermal Diffusion option.

See Section  8.9.2 for details.

7.   Enabling KINetics from Reaction Design for laminar reactions, will allow you to use the proprietary reaction-rate utilities and solution algorithms from Reaction Design, which is based on and compatible with their CHEMKIN technology [ 178]. For EDC Turbulence-Chemistry Interaction and the Composition PDF Transport model, enabling the KINetics from Reaction Design option will allow you to use reaction rates from Reaction Design's KINetics module, instead of the default FLUENT reaction rates. FLUENT's ISAT algorithm is employed to integrate these rates. Please refer to the KINetics for Fluent manual [ 3] from Reaction Design for details on the chemistry formulation options. For more information, or to obtain a license to the Fluent/KINetics module, please contact Reaction Design at info@reactiondesign.com or +1 858-550-1920, or go to http://www.reactiondesign.com


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