Contents

• About This Document
• 1. Overview
  • 1.1 What is a User-Defined Function (UDF)?
  • 1.2 Why Use UDFs?
  • 1.3 Limitations
  • 1.4 Defining Your UDF Using DEFINE Macros
    • 1.4.1 Including the udf.h Header File in Your Source File
  • 1.5 Interpreting and Compiling UDFs
    • 1.5.1 Differences Between Interpreted and Compiled UDFs
  • 1.6 Hooking UDFs to Your ANSYS FLUENT Model
  • 1.7 Mesh Terminology
  • 1.8 Data Types in ANSYS FLUENT
  • 1.9 UDF Calling Sequence in the Solution Process
  • 1.10 Special Considerations for Multiphase UDFs
    • 1.10.1 Multiphase-specific Data Types
• 2. DEFINE Macros
  • 2.1 Introduction
  • 2.2 General Purpose DEFINE Macros
    • 2.2.1 DEFINE_ADJUST
    • 2.2.2 DEFINE_DELTAT
    • 2.2.3 DEFINE_EXECUTE_AT_END
    • 2.2.4 DEFINE_EXECUTE_AT_EXIT
    • 2.2.5 DEFINE_EXECUTE_FROM_GUI
    • 2.2.6 DEFINE_EXECUTE_ON_LOADING
    • 2.2.7 DEFINE_EXECUTE_AFTER_CASE/DATA
    • 2.2.8 DEFINE_INIT
    • 2.2.9 DEFINE_ON_DEMAND
    • 2.2.10 DEFINE_RW_FILE
  • 2.3 Model-Specific DEFINE Macros
    • 2.3.1 DEFINE_CHEM_STEP
    • 2.3.2 DEFINE_CPHI
    • 2.3.3 DEFINE_DIFFUSIVITY
    • 2.3.4 DEFINE_DOM_DIFFUSE_REFLECTIVITY
    • 2.3.5 DEFINE_DOM_SOURCE
    • 2.3.6 DEFINE_DOM_SPECULAR_REFLECTIVITY
    • 2.3.7 DEFINE_EMISSIVITY_WEIGHTING_FACTOR
    • 2.3.8 DEFINE_GRAY_BAND_ABS_COEFF
    • 2.3.9 DEFINE_HEAT_FLUX
    • 2.3.10 DEFINE_IGNITE_SOURCE
    • 2.3.11 DEFINE_NET_REACTION_RATE
    • 2.3.12 DEFINE_NOX_RATE
    • 2.3.13 DEFINE_PR_RATE
    • 2.3.14 DEFINE_PRANDTL UDFs
    • 2.3.15 DEFINE_PROFILE
    • 2.3.16 DEFINE_PROPERTY UDFs
    • 2.3.17 DEFINE_SCAT_PHASE_FUNC
    • 2.3.18 DEFINE_SOLAR_INTENSITY
    • 2.3.19 DEFINE_SOURCE
    • 2.3.20 DEFINE_SOX_RATE
    • 2.3.21 DEFINE_SPECIFIC_HEAT
    • 2.3.22 DEFINE_SR_RATE
    • 2.3.23 DEFINE_TRANS UDFs
    • 2.3.24 DEFINE_TURB_PREMIX_SOURCE
    • 2.3.25 DEFINE_TURB_SCHMIDT UDF
    • 2.3.26 DEFINE_TURBULENT_VISCOSITY
    • 2.3.27 DEFINE_VR_RATE
    • 2.3.28 DEFINE_WALL_FUNCTIONS
  • 2.4 Multiphase DEFINE Macros
    • 2.4.1 DEFINE_CAVITATION_RATE
    • 2.4.2 DEFINE_EXCHANGE_PROPERTY
    • 2.4.3 DEFINE_HET_RXN_RATE
    • 2.4.4 DEFINE_MASS_TRANSFER
    • 2.4.5 DEFINE_VECTOR_EXCHANGE_PROPERTY
  • 2.5 Discrete Phase Model (DPM) DEFINE Macros
    • 2.5.1 DEFINE_DPM_BC
    • 2.5.2 DEFINE_DPM_BODY_FORCE
    • 2.5.3 DEFINE_DPM_DRAG
    • 2.5.4 DEFINE_DPM_EROSION
    • 2.5.5 DEFINE_DPM_HEAT_MASS
    • 2.5.6 DEFINE_DPM_INJECTION_INIT
    • 2.5.7 DEFINE_DPM_LAW
    • 2.5.8 DEFINE_DPM_OUTPUT
    • 2.5.9 DEFINE_DPM_PROPERTY
    • 2.5.10 DEFINE_DPM_SCALAR_UPDATE
    • 2.5.11 DEFINE_DPM_SOURCE
    • 2.5.12 DEFINE_DPM_SPRAY_COLLIDE
    • 2.5.13 DEFINE_DPM_SWITCH
    • 2.5.14 DEFINE_DPM_TIMESTEP
    • 2.5.15 DEFINE_DPM_VP_EQUILIB
  • 2.6 Dynamic Mesh DEFINE Macros
    • 2.6.1 DEFINE_CG_MOTION
    • 2.6.2 DEFINE_DYNAMIC_ZONE_PROPERTY
    • 2.6.3 DEFINE_GEOM
    • 2.6.4 DEFINE_GRID_MOTION
    • 2.6.5 DEFINE_SDOF_PROPERTIES
  • 2.7 User-Defined Scalar (UDS) Transport Equation DEFINE Macros
    • 2.7.1 Introduction
    • 2.7.2 DEFINE_ANISOTROPIC_DIFFUSIVITY
    • 2.7.3 DEFINE_UDS_FLUX
    • 2.7.4 DEFINE_UDS_UNSTEADY
• 3. Additional Macros for Writing UDFs
  • 3.1 Introduction
  • 3.2 Data Access Macros
    • 3.2.1 Axisymmetric Considerations for Data Access Macros
    • 3.2.2 Node Macros
    • 3.2.3 Cell Macros
    • 3.2.4 Face Macros
    • 3.2.5 Connectivity Macros
    • 3.2.6 Special Macros
    • 3.2.7 Model-Specific Macros
    • 3.2.8 User-Defined Scalar (UDS) Transport Equation Macros
    • 3.2.9 User-Defined Memory (UDM) Macros
  • 3.3 Looping Macros
    • 3.3.1 Multiphase Looping Macros
    • 3.3.2 Advanced Multiphase Macros
  • 3.4 Vector and Dimension Macros
    • 3.4.1 Macros for Dealing with Two and Three Dimensions
    • 3.4.2 The ND Macros
    • 3.4.3 The NV Macros
    • 3.4.4 Vector Operation Macros
  • 3.5 Time-Dependent Macros
  • 3.6 Scheme Macros
    • 3.6.1 Defining a Scheme Variable in the Text Interface
    • 3.6.2 Accessing a Scheme Variable in the Text Interface
    • 3.6.3 Changing a Scheme Variable to Another Value in the Text Interface
    • 3.6.4 Accessing a Scheme Variable in a UDF
  • 3.7 Input/Output Macros
  • 3.8 Miscellaneous Macros
• 4. Interpreting UDFs
  • 4.1 Introduction
    • 4.1.1 Location of the udf.h File
    • 4.1.2 Limitations
  • 4.2 Interpreting a UDF Source File Using the Interpreted UDFs Dialog Box
  • 4.3 Common Errors Made While Interpreting A Source File
• 5. Compiling UDFs
  • 5.1 Introduction
    • 5.1.1 Location of the udf.h File
    • 5.1.2 Compilers
  • 5.2 Compiling a UDF Using the GUI
  • 5.3 Compile a UDF Using the TUI
    • 5.3.1 Set Up the Directory Structure
    • 5.3.2 Build the UDF Library
    • 5.3.3 Load the UDF Library
  • 5.4 Link Precompiled Object Files From Non- ANSYS FLUENT Sources
    • 5.4.1 Example - Link Precompiled Objects to ANSYS FLUENT
  • 5.5 Load and Unload Libraries Using the UDF Library Manager Dialog Box
  • 5.6 Common Errors When Building and Loading a UDF Library
  • 5.7 Special Considerations for Parallel ANSYS FLUENT
• 6. Hooking UDFs to ANSYS FLUENT
  • 6.1 Hooking General Purpose UDFs
    • 6.1.1 Hooking DEFINE_ADJUST UDFs
    • 6.1.2 Hooking DEFINE_DELTAT UDFs
    • 6.1.3 Hooking DEFINE_EXECUTE_AT_END UDFs
    • 6.1.4 Hooking DEFINE_EXECUTE_AT_EXIT UDFs
    • 6.1.5 Hooking DEFINE_INIT UDFs
    • 6.1.6 Hooking DEFINE_ON_DEMAND UDFs
    • 6.1.7 Hooking DEFINE_RW_FILE UDFs
    • 6.1.8 User-Defined Memory Storage
  • 6.2 Hooking Model-Specific UDFs
    • 6.2.1 Hooking DEFINE_CHEM_STEP UDFs
    • 6.2.2 Hooking DEFINE_CPHI UDFs
    • 6.2.3 Hooking DEFINE_DIFFUSIVITY UDFs
    • 6.2.4 Hooking DEFINE_DOM_DIFFUSE_REFLECTIVITY UDFs
    • 6.2.5 Hooking DEFINE_DOM_SOURCE UDFs
    • 6.2.6 Hooking DEFINE_DOM_SPECULAR_REFLECTIVITY UDFs
    • 6.2.7 Hooking DEFINE_EMISSIVITY_WEIGHTING_FACTOR UDFs
    • 6.2.8 Hooking DEFINE_GRAY_BAND_ABS_COEFF UDFs
    • 6.2.9 Hooking DEFINE_HEAT_FLUX UDFs
    • 6.2.10 Hooking DEFINE_IGNITE_SOURCE UDFs
    • 6.2.11 Hooking DEFINE_NET_REACTION_RATE UDFs
    • 6.2.12 Hooking DEFINE_NOX_RATE UDFs
    • 6.2.13 Hooking DEFINE_PR_RATE UDFs
    • 6.2.14 Hooking DEFINE_PRANDTL UDFs
    • 6.2.15 Hooking DEFINE_PROFILE UDFs
    • 6.2.16 Hooking DEFINE_PROPERTY UDFs
    • 6.2.17 Hooking DEFINE_SCAT_PHASE_FUNC UDFs
    • 6.2.18 Hooking DEFINE_SOLAR_INTENSITY UDFs
    • 6.2.19 Hooking DEFINE_SOURCE UDFs
    • 6.2.20 Hooking DEFINE_SOX_RATE UDFs
    • 6.2.21 Hooking DEFINE_SPECIFIC_HEAT UDFs
    • 6.2.22 Hooking DEFINE_SR_RATE UDFs
    • 6.2.23 Hooking DEFINE_TRANS UDFs
    • 6.2.24 Hooking DEFINE_TURB_PREMIX_SOURCE UDFs
    • 6.2.25 Hooking DEFINE_TURB_SCHMIDT UDFs
    • 6.2.26 Hooking DEFINE_TURBULENT_VISCOSITY UDFs
    • 6.2.27 Hooking DEFINE_VR_RATE UDFs
    • 6.2.28 Hooking DEFINE_WALL_FUNCTIONS UDFs
  • 6.3 Hooking Multiphase UDFs
    • 6.3.1 Hooking DEFINE_CAVITATION_RATE UDFs
    • 6.3.2 Hooking DEFINE_EXCHANGE_PROPERTY UDFs
    • 6.3.3 Hooking DEFINE_HET_RXN_RATE UDFs
    • 6.3.4 Hooking DEFINE_MASS_TRANSFER UDFs
    • 6.3.5 Hooking DEFINE_VECTOR_EXCHANGE_PROPERTY UDFs
  • 6.4 Hooking Discrete Phase Model (DPM) UDFs
    • 6.4.1 Hooking DEFINE_DPM_BC UDFs
    • 6.4.2 Hooking DEFINE_DPM_BODY_FORCE UDFs
    • 6.4.3 Hooking DEFINE_DPM_DRAG UDFs
    • 6.4.4 Hooking DEFINE_DPM_EROSION UDFs
    • 6.4.5 Hooking DEFINE_DPM_HEAT_MASS UDFs
    • 6.4.6 Hooking DEFINE_DPM_INJECTION_INIT UDFs
    • 6.4.7 Hooking DEFINE_DPM_LAW UDFs
    • 6.4.8 Hooking DEFINE_DPM_OUTPUT UDFs
    • 6.4.9 Hooking DEFINE_DPM_PROPERTY UDFs
    • 6.4.10 Hooking DEFINE_DPM_SCALAR_UPDATE UDFs
    • 6.4.11 Hooking DEFINE_DPM_SOURCE UDFs
    • 6.4.12 Hooking DEFINE_DPM_SPRAY_COLLIDE UDFs
    • 6.4.13 Hooking DEFINE_DPM_SWITCH UDFs
    • 6.4.14 Hooking DEFINE_DPM_TIMESTEP UDFs
    • 6.4.15 Hooking DEFINE_DPM_VP_EQUILIB UDFs
  • 6.5 Hooking Dynamic Mesh UDFs
    • 6.5.1 Hooking DEFINE_CG_MOTION UDFs
    • 6.5.2 Hooking DEFINE_DYNAMIC_ZONE_PROPERTY UDFs
    • 6.5.3 Hooking DEFINE_GEOM UDFs
    • 6.5.4 Hooking DEFINE_GRID_MOTION UDFs
    • 6.5.5 Hooking DEFINE_SDOF_PROPERTIES UDFs
  • 6.6 Hooking User-Defined Scalar (UDS) Transport Equation UDFs
    • 6.6.1 Hooking DEFINE_ANISOTROPIC_DIFFUSIVITY UDFs
    • 6.6.2 Hooking DEFINE_UDS_FLUX UDFs
    • 6.6.3 Hooking DEFINE_UDS_UNSTEADY UDFs
  • 6.7 Common Errors While Hooking a UDF to ANSYS FLUENT
• 7. Parallel Considerations
  • 7.1 Overview of Parallel ANSYS FLUENT
    • 7.1.1 Command Transfer and Communication
  • 7.2 Cells and Faces in a Partitioned Mesh
  • 7.3 Parallelizing Your Serial UDF
  • 7.4 Parallelization of Discrete Phase Model (DPM) UDFs
  • 7.5 Macros for Parallel UDFs
    • 7.5.1 Compiler Directives
    • 7.5.2 Communicating Between the Host and Node Processes
    • 7.5.3 Predicates
    • 7.5.4 Global Reduction Macros
    • 7.5.5 Looping Macros
    • 7.5.6 Cell and Face Partition ID Macros
    • 7.5.7 Message Displaying Macros
    • 7.5.8 Message Passing Macros
    • 7.5.9 Macros for Exchanging Data Between Compute Nodes
  • 7.6 Limitations of Parallel UDFs
  • 7.7 Process Identification
  • 7.8 Parallel UDF Example
  • 7.9 Writing Files in Parallel
• 8. Examples
  • 8.1 Step-By-Step UDF Example
    • 8.1.1 Process Overview
    • 8.1.2 Step 1: Define Your Problem
    • 8.1.3 Step 2: Create a C Source File
    • 8.1.4 Step 3: Start ANSYS FLUENT and Read (or Set Up) the Case File
    • 8.1.5 Step 4: Interpret or Compile the Source File
    • 8.1.6 Step 5: Hook the UDF to ANSYS FLUENT
    • 8.1.7 Step 6: Run the Calculation
    • 8.1.8 Step 7: Analyze the Numerical Solution and Compare to Expected Results
  • 8.2 Detailed UDF Examples
    • 8.2.1 Boundary Conditions
    • 8.2.2 Source Terms
    • 8.2.3 Physical Properties
    • 8.2.4 Reaction Rates
    • 8.2.5 User-Defined Scalars
    • 8.2.6 User-Defined Real Gas Models
• A. C Programming Basics
  • A.1 Introduction
  • A.2 Commenting Your C Code
  • A.3 C Data Types in ANSYS FLUENT
  • A.4 Constants
  • A.5 Variables
    • A.5.1 Declaring Variables
    • A.5.2 External Variables
    • A.5.3 Static Variables
  • A.6 User-Defined Data Types
  • A.7 Casting
  • A.8 Functions
  • A.9 Arrays
  • A.10 Pointers
  • A.11 Control Statements
    • A.11.1 if Statement
    • A.11.2 if-else Statement
    • A.11.3 for Loops
  • A.12 Common C Operators
    • A.12.1 Arithmetic Operators
    • A.12.2 Logical Operators
  • A.13 C Library Functions
    • A.13.1 Trigonometric Functions
    • A.13.2 Miscellaneous Mathematical Functions
    • A.13.3 Standard I/O Functions
  • A.14 Preprocessor Directives
  • A.15 Comparison with FORTRAN
• B. DEFINE Macro Definitions
  • B.1 General Solver DEFINE Macros
  • B.2 Model-Specific DEFINE Macro Definitions
  • B.3 Multiphase DEFINE Macros
  • B.4 Dynamic Mesh Model DEFINE Macros
  • B.5 Discrete Phase Model DEFINE Macros
  • B.6 User-Defined Scalar (UDS) DEFINE Macros
• C. Quick Reference Guide for Multiphase DEFINE Macros
  • C.1 VOF Model
  • C.2 Mixture Model
  • C.3 Eulerian Model - Laminar Flow
  • C.4 Eulerian Model - Mixture Turbulence Flow
  • C.5 Eulerian Model - Dispersed Turbulence Flow
  • C.6 Eulerian Model - Per Phase Turbulence Flow
• Bibliography
• Index