6.3.2 Hooking DEFINE_EXCHANGE_PROPERTY UDFs

After you have interpreted (Chapter  4) or compiled (Chapter  5) your DEFINE_EXCHANGE_RATE UDF, the name of the function you supplied as a DEFINE macro argument will become visible and selectable in ANSYS FLUENT.

To hook an exchange property UDF to ANSYS FLUENT, first open the Multiphase Model dialog box.

Models Multiphase Edit...

Customized mass transfer UDFs can be applied to VOF, Mixture, and Eulerian multiphase models. Drag coefficient UDFs can be applied to Mixture and Eulerian models, while heat transfer and lift coefficient UDFs can be applied only to the Eulerian model. Select the appropriate model from the Model list in the Multiphase Model dialog box and click OK.

Make sure that you enable Slip Velocity in the Mixture Parameters group box in the Multiphase Model dialog box in order to display the drag coefficient for the Mixture model.

Next, open the Phase Interaction dialog box (Figure  6.3.3).

Phases Interaction...

Figure 6.3.3: The Phase Interaction Dialog Box

Click the appropriate tab (e.g., Drag) in the Phase Interaction dialog box, and select user-defined from the drop-down list for the corresponding exchange property (e.g., Drag Coefficient) that you desire. This will open the User-Defined Functions dialog box .

Figure 6.3.4: The User-Defined Functions Dialog Box

Select the function name (e.g., custom_drag::libudf) from the list of UDFs displayed in the User-Defined Functions dialog box (Figure  6.3.4) and click OK. The function name will then be displayed in a text box under the exchange property in the Phase Interaction dialog box. Click OK to close the Phase Interaction dialog box.

See Section  2.4.2 for details about DEFINE_EXCHANGE_PROPERTY functions.