6.2.1 Hooking DEFINE_CHEM_STEP UDFs

After you have interpreted (Chapter  4) or compiled (Chapter  5) your DEFINE_CHEM_STEP UDF, the name of the function you supplied as a DEFINE macro argument will become visible and selectable in the User-Defined Function Hooks dialog box (Figure  6.2.1) in ANSYS FLUENT.

To hook the UDF to ANSYS FLUENT, first set up the species transport and combustion models in the Species Model dialog box.

Models Species Edit...

Note that chemistry step UDFs may only be used with the laminar finite-rate model (with stiff chemistry enabled), the EDC model, or the PDF Transport model. Therefore, you must use one of the following groups of settings in the Species Model dialog box:

• To enable the laminar finite-rate model, select Species Transport, enable Volumetric in the Reactions group box, select Laminar Finite-Rate in the Turbulence-Chemistry Interaction group box, and enable Stiff Chemistry Solver in the Options group box.

• To enable the EDC model, select Species Transport, enable Volumetric in the Reactions group box, and select Eddy-Dissipation Concept in the Turbulence-Chemistry Interaction group box.

• To enable the PDF Transport model, select Composition PDF Transport and enable Volumetric in the Reactions group box.

Next, open the User-Defined Function Hooks dialog box. (Figure  6.2.1)

Define $\rightarrow$ User-Defined $\rightarrow$ Function Hooks...

Figure 6.2.1: The User-Defined Function Hooks Dialog Box

Select the function name (e.g., user_chem_step::libudf) in the Chemistry Step drop-down list in the User-Defined Function Hooks dialog box, and click OK.

See Section  2.3.1 for details about defining DEFINE_CHEM_STEP functions.