Source: ANSYS HELP
User-defined functions (UDFs) allow you to customize ANSYS Fluent and can significantly enhance its capabilities
Download Files: UDF1
A user-defined function, or UDF, is a C function that can be dynamically loaded with the ANSYS Fluent solver to enhance its standard features. For example, you can use a UDF to: • Customize boundary conditions, material property definitions, surface and volume reaction rates, source terms in ANSYS Fluent transport equations, source terms in user-defined scalar (UDS) transport equations, diffusivity functions, and so on. • Adjust computed values on a once-per-iteration basis. • Initialize of a solution. • Perform asynchronous (on-demand) execution of a UDF. • Execute at the end of an iteration, upon exit from ANSYS Fluent, or upon loading of a compiled UDF library. • Enhance postprocessing. • Enhance existing ANSYS Fluent models (such as discrete phase model, multiphase mixture model, discrete ordinates radiation model).