This chapter contains an overview of user-defined functions (UDFs) and their usage in Ansys Fluent. UDF functionality is described in the following sections:

• 1.1. What is a User-Defined Function?
• 1.2. Limitations
• 1.3. Defining Your UDF Using DEFINE Macros
• 1.4. Interpreting and Compiling UDFs
• 1.5. Hooking UDFs to Your Ansys Fluent Model
• 1.6. Mesh Terminology
• 1.7. Data Types in Ansys Fluent
• 1.8. UDF Calling Sequence in the Solution Process
• 1.9. Special Considerations for Multiphase UDFs