ANSYS Fluent Customization Manual
Release 16.2ANSYS, Inc.
July 2015Southpointe
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Table of Contents
Using This Manual ..................................................................................................................................... xxv
1.The Contents of This Manual ............................................................................................................. xxv
2.The Contents of the Fluent Manuals ................................................................................................ xxvii
3. Typographical Conventions ........................................................................................................... xxviii
4. Mathematical Conventions ............................................................................................................... xxx
5. Technical Support ........................................................................................................................... xxxi
I. Creating and Using User Defined Functions ............................................................................................ 1
1. Overview of User-Defined Functions (UDFs) .................................................................................... 3
1.1. What is a User-Defined Function? ................................................................................................ 3
1.2. Limitations ................................................................................................................................. 4
1.3. Defining Your UDF Using DEFINE Macros ................................................................................... 4
1.3.1. Including the udf.h Header File in Your Source File ........................................................... 5
1.4. Interpreting and Compiling UDFs ................................................................................................ 6
1.4.1. Compiled UDFs .................................................................................................................. 6
1.4.2. Interpreted UDFs ............................................................................................................... 6
1.4.3. Differences Between Interpreted and Compiled UDFs ......................................................... 6
1.5. Hooking UDFs to Your ANSYS Fluent Model ................................................................................. 7
1.6. Mesh Terminology ...................................................................................................................... 8
1.7. Data Types in ANSYS Fluent ......................................................................................................... 9
1.8. UDF Calling Sequence in the Solution Process ........................................................................... 10
1.8.1. Pressure-Based Segregated Solver .................................................................................... 11
1.8.2. Pressure-Based Coupled Solver ......................................................................................... 12
1.8.3. Density-Based Solver ........................................................................................................ 13
1.9. Special Considerations for Multiphase UDFs .............................................................................. 14
1.9.1. Multiphase-specific Data Types ......................................................................................... 14
2. DEFINE Macros ............................................................................................................................... 17
2.1. Introduction ............................................................................................................................. 17
2.2. General Purpose DEFINE Macros ............................................................................................. 17
2.2.1. DEFINE_ADJUST ........................................................................................................... 18
2.2.1.1. Description ............................................................................................................. 18
2.2.1.2. Usage ...................................................................................................................... 19
2.2.1.3. Example 1 ............................................................................................................... 19
2.2.1.4. Example 2 ............................................................................................................... 20
2.2.1.5. Hooking an Adjust UDF to ANSYS Fluent .................................................................. 20
2.2.2. DEFINE_DELTAT ........................................................................................................... 20
2.2.2.1. Description ............................................................................................................. 20
2.2.2.2. Usage ...................................................................................................................... 20
2.2.2.3. Example .................................................................................................................. 21
2.2.2.4. Hooking an Adaptive Time Step UDF to ANSYS Fluent .............................................. 21
2.2.3. DEFINE_EXECUTE_AT_END .......................................................................................... 21
2.2.3.1. Description ............................................................................................................. 21
2.2.3.2. Usage ...................................................................................................................... 22
2.2.3.3. Example .................................................................................................................. 22
2.2.3.4. Hooking an Execute-at-End UDF to ANSYS Fluent ..................................................... 22
2.2.4. DEFINE_EXECUTE_AT_EXIT ....................................................................................... 23
2.2.4.1. Description ............................................................................................................. 23
2.2.4.2. Usage ...................................................................................................................... 23
2.2.4.3. Hooking an Execute-at-Exit UDF to ANSYS Fluent ..................................................... 23
2.2.5. DEFINE_EXECUTE_FROM_GUI ..................................................................................... 23
2.2.5.1. Description ............................................................................................................. 23
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2.2.5.2. Usage ...................................................................................................................... 23
2.2.5.3. Example .................................................................................................................. 24
2.2.5.4. Hooking an Execute From GUI UDF to ANSYS Fluent ................................................. 25
2.2.6. DEFINE_EXECUTE_ON_LOADING ................................................................................. 25
2.2.6.1. Description ............................................................................................................. 25
2.2.6.2. Usage ...................................................................................................................... 25
2.2.6.3. Example 1 ............................................................................................................... 25
2.2.6.4. Example 2 ............................................................................................................... 26
2.2.6.5. Hooking an Execute On Loading UDF to ANSYS Fluent ............................................. 27
2.2.7. DEFINE_EXECUTE_AFTER_CASE/DATA ...................................................................... 27
2.2.7.1. Description ............................................................................................................. 27
2.2.7.2. Usage ...................................................................................................................... 27
2.2.7.3. Example .................................................................................................................. 28
2.2.7.4. Hooking an Execute After Reading Case and Data File UDF to ANSYS Fluent .............. 28
2.2.8. DEFINE_INIT ................................................................................................................ 28
2.2.8.1. Description ............................................................................................................. 28
2.2.8.2. Usage ...................................................................................................................... 28
2.2.8.3. Example .................................................................................................................. 29
2.2.8.4. Hooking an Initialization UDF to ANSYS Fluent ......................................................... 29
2.2.9. DEFINE_ON_DEMAND ..................................................................................................... 29
2.2.9.1. Description ............................................................................................................. 29
2.2.9.2. Usage ...................................................................................................................... 30
2.2.9.3. Example .................................................................................................................. 30
2.2.9.4. Hooking an On-Demand UDF to ANSYS Fluent ......................................................... 31
2.2.10. DEFINE_OUTPUT_PARAMETER ................................................................................... 31
2.2.10.1. Description ............................................................................................................ 31
2.2.10.2. Usage .................................................................................................................... 31
2.2.10.3. Example ................................................................................................................ 32
2.2.10.4. Hooking an Output Parameter UDF to ANSYS Fluent .............................................. 32
2.2.11. DEFINE_RW_FILE ....................................................................................................... 33
2.2.11.1. Description ............................................................................................................ 33
2.2.11.2. Usage .................................................................................................................... 33
2.2.11.3. Example ................................................................................................................ 33
2.2.11.4. Hooking a Read/Write Case or Data File UDF to ANSYS Fluent ................................. 34
2.2.12. DEFINE_RW_HDF_FILE .............................................................................................. 34
2.2.12.1. Description ............................................................................................................ 34
2.2.12.2. Usage .................................................................................................................... 34
2.2.12.3. Helper Functions ................................................................................................... 34
2.2.12.4. Examples ............................................................................................................... 39
2.2.12.5. Hooking a Read/Write HDF Case or Data File UDF to ANSYS Fluent .......................... 40
2.3. Model-Specific DEFINE Macros ................................................................................................ 40
2.3.1. DEFINE_ANISOTROPIC_CONDUCTIVITY .................................................................... 47
2.3.1.1. Description ............................................................................................................. 47
2.3.1.2. Usage ...................................................................................................................... 47
2.3.1.3. Example .................................................................................................................. 47
2.3.1.4. Hooking an Anisotropic Conductivity UDF to ANSYS Fluent ...................................... 48
2.3.2. DEFINE_CHEM_STEP ..................................................................................................... 49
2.3.2.1. Description ............................................................................................................. 49
2.3.2.2. Usage ...................................................................................................................... 49
2.3.2.3. Example .................................................................................................................. 50
2.3.2.4. Hooking a Chemistry Step UDF to ANSYS Fluent ....................................................... 50
2.3.3. DEFINE_CPHI ................................................................................................................ 50
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2.3.3.1. Description ............................................................................................................. 50
2.3.3.2. Usage ...................................................................................................................... 50
2.3.3.3. Hooking a Mixing Constant UDF to ANSYS Fluent ..................................................... 51
2.3.4. DEFINE_DIFFUSIVITY ................................................................................................ 51
2.3.4.1. Description ............................................................................................................. 51
2.3.4.2. Usage ...................................................................................................................... 51
2.3.4.3. Example .................................................................................................................. 51
2.3.4.4. Hooking a Diffusivity UDF to ANSYS Fluent .............................................................. 52
2.3.5. DEFINE_DOM_DIFFUSE_REFLECTIVITY .................................................................... 52
2.3.5.1. Description ............................................................................................................. 52
2.3.5.2. Usage ...................................................................................................................... 52
2.3.5.3. Example .................................................................................................................. 53
2.3.5.4. Hooking a Discrete Ordinates Model (DOM) Diffuse Reflectivity UDF to ANSYS Flu-
ent ..................................................................................................................................... 53
2.3.6. DEFINE_DOM_SOURCE .................................................................................................. 54
2.3.6.1. Description ............................................................................................................. 54
2.3.6.2. Usage ...................................................................................................................... 54
2.3.6.3. Example .................................................................................................................. 54
2.3.6.4. Hooking a DOM Source UDF to ANSYS Fluent ........................................................... 55
2.3.7. DEFINE_DOM_SPECULAR_REFLECTIVITY ................................................................. 55
2.3.7.1. Description ............................................................................................................. 55
2.3.7.2. Usage ...................................................................................................................... 55
2.3.7.3. Example .................................................................................................................. 56
2.3.7.4. Hooking a Discrete Ordinates Model (DOM) Specular Reflectivity UDF to ANSYS Flu-
ent ..................................................................................................................................... 56
2.3.8. DEFINE_ECFM_SOURCE ................................................................................................ 57
2.3.8.1. Description ............................................................................................................. 57
2.3.8.2. Usage ...................................................................................................................... 57
2.3.8.3. Example .................................................................................................................. 57
2.3.8.4. Hooking an ECFM Flame Density Area Source UDF to ANSYS Fluent .......................... 58
2.3.9. DEFINE_ECFM_SPARK_SOURCE ................................................................................... 58
2.3.9.1. Description ............................................................................................................. 58
2.3.9.2. Usage ...................................................................................................................... 58
2.3.9.3. Example .................................................................................................................. 59
2.3.9.4. Hooking an ECFM Spark Source UDF to ANSYS Fluent ............................................... 59
2.3.10. DEFINE_EMISSIVITY_WEIGHTING_FACTOR ........................................................... 59
2.3.10.1. Description ............................................................................................................ 59
2.3.10.2. Usage .................................................................................................................... 59
2.3.10.3. Example ................................................................................................................ 60
2.3.10.4. Hooking an Emissivity Weighting Factor UDF to ANSYS Fluent ................................ 60
2.3.11. DEFINE_ZONE_MOTION .............................................................................................. 60
2.3.11.1. Description ............................................................................................................ 60
2.3.11.2. Usage .................................................................................................................... 60
2.3.11.3. Example ................................................................................................................ 61
2.3.11.4. Hooking a Frame Motion UDF to ANSYS Fluent ....................................................... 62
2.3.12. DEFINE_GRAY_BAND_ABS_COEFF ............................................................................. 62
2.3.12.1. Description ............................................................................................................ 62
2.3.12.2. Usage .................................................................................................................... 62
2.3.12.3. Example ................................................................................................................ 62
2.3.12.4. Hooking a Gray Band Coefficient UDF to ANSYS Fluent ........................................... 63
2.3.13. DEFINE_HEAT_FLUX ................................................................................................... 63
2.3.13.1. Description ............................................................................................................ 63
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Release 16.2 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.
Customization Manual
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