User-defined k
 

Dear all,
I want to use UDF to modify the kinetic energy (k) field in the locations where the y plus value is less than 20.

is there anyone who can help me?
thanks

You can define a new source equation (using DEFINE_SOURCE), and inside that source add an if statement to take care of the y+<20 part. Then you'll hook that source equation to the k equation (DEFINE - BOUNDARY CONDITIONS - FLUID).

I'd be happy to help you along if you have more specific questions.

thank you very much to have answer for me...
I have use a udf with define_adjust, is that not correct!

Yes, you can use an define_adjust as well, there are several ways to approach your problem.
You can use define_adjust to adjust the k value.
Or, you can use define_source to define a NEW k value, and set your new value to FLUENT's k.

define_source
 

Ok well, please if i need to use define_source and when i will to hook my source equation in DEFINE - BOUNDARY CONDITIONS - FLUID in this panel what I must do?
thanks

Hi,
DEFINE_WALL_FUNCTIONS should be used for specifying user defined wall functions. Hope you are using k-epsilon model to define turbulence. Please go through the online doc for number of arguments for this function.
You cannot use DEFINE_SOURCE/ DEFINE_ADJUST for specifying user defined wall functions.
Regards,