User-Defined Function (UDF) Concepts in ANSYS Fluent

Introduction to UDF Concepts
This video aims to talk about User-Defined Function (UDF) Concepts. This lesson will give you a general introduction to the UDF and an overview of using UDF programming in ANSYS Fluent. This product is the first chapter of the UDF training course. We fully and comprehensively introduce you to UDF writing and its importance in Ansys Fluent software.
First, we teach how to run UDF in Fluent software. For this, you can use two methods:
Compiling
Interpreting
When you use UDF, there is a link between the UDF commands and the internal data of the Fluent software. So, we introduce a concept called Mesh Terminology. Therefore, we define concepts such as Mesh Components, Structure Data, Threads, Pointers, etc. To program UDF, we must use predefined Macros in Fluent Ansys. So, UDF can be classified based on the type of macros used.
In this training chapter, we introduce different types of commonly used macros. Some of them are:
General Purpose DEFINE Macros
Model-Specific DEFIENE Macros
Multiphase DEFINE Macros
Discrete Phase Model (DPM) DEFINE Macros
Dynamic Mesh DEFINE Macros
Each category has several examples of macros, and we introduce some commonly used examples. Then, we explain the use and function of each of these macros. Each of these macros consists of several arguments. We introduce each of these arguments and explain their function.
Some examples of general purpose macros category:
DEFINE_ADJUST
DEFINE_DELTAT
DEFINE_EXECUTE_AT_END
DEFINE_INIT
Some examples of model-specific macros category:
DEFINE_PROFILE
DEFINE_PROPERTY
DEFINE_SOURCE
DEFINE_PRANDTL
Some examples of multiphase macros category:
DEFINE_CAVITATION_RATE
DEFINE_EXCHANGE_PROPERTY
DEFINE_MASS_TRANSFER
Some examples of discrete phase model (DPM) macros category:
DEFINE_DPM_BC
DEFINE_DPM_DRAG
DEFINE_DPM_EROSION
Some examples of dynamic mesh macros category:
DEFINE_CG_MOTION
DEFINE_SDOF_PROPERTIES
DEFINE_GRID_MOTION
In the next section, we introduce some examples of additional macros:
Data Access Macros
Looping Macros
Vector and Dimensions Macros
Time-Dependent Macros

[@viveksankurubhukta6241]

I am running a 2D transient simulation(VOF Fluent) in which vapor bubbles are generated at the bottom surface of a rectangular domain that is initially full of water with heat flux given at the bottom wall. I was trying to patch a single vapor bubble by creating a hemispherical region. I can see my volume fraction contour with the bubble after patching a hemispherical region at the bottom of the liquid. The simulation is also running perfectly when I click on "Run Calculation".
When I do this same bubble patch operation through a DEFINE_INIT UDF, I can see the bubble getting patched in the vapor phase contour, but the calculation is not running. It is giving the following error in the 1st iteration itself.
Divergence detected in AMG solver: vof-1
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: temperature
UDF code
#include "udf.h"
DEFINE_INIT (init2, domain1)
{
Message("solution initialised");
cell_t cell;
Thread *cell_thread;
Domain *subdomain;
int phase_domain_index;
//Initialisation of heater layer
sub_domain_loop(subdomain, domain1, phase_domain_index)
{
if(DOMAIN_ID(subdomain) == 2)
{
thread_loop_c (cell_thread,subdomain)
{
begin_c_loop_all (cell,cell_thread)
{
real arr[ND_ND];
C_CENTROID(arr,cell,cell_thread);
if (sqrt(ND_SUM(pow(arr[0],2),pow(arr[1],2), pow(arr[2],2)))

[@abdeldjalilbait4327]

Well done, I appreciate your efforts and looking for more description and examples on UDF
Thanks bro.

[@MRCFD]

www.mr-cfd.com/shop/user-defined-function-udf-cfd-simulation-training-course/ you can benefit from this course

[@SherlockHolmes-dx7do]

You forget DEFINE_ON_DEMAND function 26:18

[@AhmedAbrarShayor]

Could you please tell me the explanation why in DEFINE_EXECUTE_AT_END explanation in the second slide at the top there shows two arguments(name,d)?

[@AbhiramP-z3x]

hi, I'm trying to vary the specific heat with respect to spatial coordinates in a micro combustor along the length.
I tried to write some udfs but they didn't worked can you help me with this.

[@aneesurrehman4135]

can you help me to write UDF for the dimensionless slip coefficient?

[@MRCFD]

you can be in touch with me via whatsapp or email [phone] [e-mail]