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Old   October 17, 2009, 12:22
Default User-defined k
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gina
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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
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Old   October 17, 2009, 18:39
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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.
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Old   October 23, 2009, 14:12
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thank you very much to have answer for me...
I have use a udf with define_adjust, is that not correct!
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Old   October 23, 2009, 18:05
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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.
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Old   October 24, 2009, 16:13
Default define_source
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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?
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Old   October 26, 2009, 08:42
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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.
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