Atharva Nagarkar
Ansys Employee


As part of the Ansys policy, employees cannot debug UDFs on the forum. However, I would suggest you to have a look at the following things.

For the macro C_UDSI, if you try to use the macro before you have specified the user-defined scalars in your Ansys Fluent model then an error will result.

3.2. Data Access Macros ( -> Check section

Please also have a look at the definition of the macro C_UDMI and how the arguments are defined at the link below.

3.2. Data Access Macros ( -> Check section

Additionally, this is the link from the Ansys manual for defining the source term. Make sure that you have correctly defined the dS[] array with respect to the dependent variable.

2.3. Model-Specific DEFINE Macros ( -> Check section 2.3.43

Lastly, these are the time dependent macros which you can use to access variables for previous timesteps.

3.5. Time-Dependent Macros (

If you are not able to access the link, please refer to this forum discussion: Using Help with links (