19.2 Steps for Using the Composition PDF Transport Model

The procedure for setting up and solving a composition PDF transport problem is outlined below, and then described in detail. Remember that only steps that are pertinent to composition PDF transport modeling are shown here. For information about inputs related to other models that you are using in conjunction with the composition PDF transport model, see the appropriate sections for those models.

1.   Read a CHEMKIN-formatted gas-phase mechanism file and the associated thermodynamic data file in the CHEMKIN Mechanism dialog box (see Section  15.1.9).

File $\rightarrow$ Import $\rightarrow$ CHEMKIN Mechanism...

If your chemical mechanism is not in CHEMKIN format, you will have to enter the mechanism into ANSYS FLUENT as described in Section  15.1.1.

2.   Enable a turbulence model.

Models Viscous Edit...

3.   Enable the Composition PDF Transport model and set the related parameters.Refer to Sections  19.3 and 19.4 for further details.

Models Species Edit...

4.   Check the material properties in the Create/Edit Materials dialog box and the reaction parameters in the Reactions dialog box. The default settings should be sufficient.

Materials

5.   Set the operating conditions, cell zone conditions, and boundary conditions.

Cell Zone Conditions Operating Conditions...

Boundary Conditions

6.   Check the solver settings.

Solution Methods

Solution Controls

The default settings should be sufficient, although it is recommended to change the discretization to second-order once the solution has converged.

7.   Initialize the solution. You may need to patch a high-temperature region to ignite the flame.

Solution Initialization Initialize

Solution Initialization Patch...

8.   Run the solution.

Run Calculation

9.   Solve the problem and perform postprocessing.

A good initial condition can reduce the solution time substantially. It is recommended to start from an existing solution calculated using the Laminar Finite-Rate, EDC model, non-premixed combustion model, or partially premixed combustion model. See Chapters  15, 16, and 18 for further information on such simulations.

This procedure is demonstrated in the PDF transport tutorial, which is available at the ser Services Center.