About This Document

User-defined functions (UDFs) allow you to customize ANSYS FLUENT and can significantly enhance its capabilities. This UDF Manual presents detailed information on how to write, compile, and use UDFs in ANSYS FLUENT. Examples have also been included, where available. General information about C programming basics is included in an appendix.

Information in this manual is presented in the following chapters:

• Chapter  1: Overview

• Chapter  2: DEFINE Macros

• Chapter  3: Additional Macros for Writing UDFs

• Chapter  4: Interpreting UDFs

• Chapter  5: Compiling UDFs

• Chapter  6: Hooking UDFs to ANSYS FLUENT

• Chapter  7: Parallel Considerations

• Chapter  8: Examples

This document provides some basic information about the C programming language (Appendix A) as it relates to user-defined functions in ANSYS FLUENT, and assumes that you are an experienced programmer in C. If you are unfamiliar with C, please consult a C language reference guide (e.g., [ 6, 9]) before you begin the process of writing UDFs and using them in your ANSYS FLUENT model.

This document does not imply responsibility on the part of ANSYS, Inc. for the accuracy or stability of solutions obtained using UDFs that are either user-generated or provided by ANSYS, Inc. Support for current license holders will be limited to guidance related to communication between a UDF and the ANSYS FLUENT solver. Other aspects of the UDF development process that include conceptual function design, implementation (writing C code), compilation and debugging of C source code, execution of the UDF, and function design verification will remain the responsibility of the UDF author.

UDF compiled libraries are specific to the computer architecture being used and the version of the ANSYS FLUENT executable being run and must be rebuilt any time ANSYS FLUENT is upgraded, your operating system changes, or the job is run on a different type of computer. Note that UDFs may need to be updated with new versions of ANSYS FLUENT.