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-   -   define wall functions (UDF) in Fluent 6.3 (https://www.cfd-online.com/Forums/fluent/47577-define-wall-functions-udf-fluent-6-3-a.html)

Alex March 11, 2008 13:32

define wall functions (UDF) in Fluent 6.3
 
Hello all,

I have been trying the example of DEFINE_WALL_FUNCTIONS in the Fluent 6.3 UDF manual (paragraph 2.3.23), but it doesn't seem to compile in Fluent. What I get in the log report is the following:

udf_names.c:8: error: 'user_log_law' undeclared here (not in a function)

udf_names.c:8: error: 'UDF_TYPE_WALL_FUNCTIONS' undeclared here (not in a function)

Could it be the case that I need to give some additional details in the UDF script?

Alex

Dave S March 24, 2008 04:39

Re: define wall functions (UDF) in Fluent 6.3
 
Before compiling the UDF in Fluent you need to start Fluent in a C++ DOS window.

Alex March 24, 2008 08:15

Re: define wall functions (UDF) in Fluent 6.3
 
Thanks for your reply,

I figured out what was the problem. I was using the udf.h file from the previous version (6.2) so I updated the new one.

Alex.


m zahid September 20, 2014 12:37

meaning of DUPLUS AND D2PLUS
 
hi,

anybody know the meaning of DUPLUS and D2PLUS. these terms are used in UDF wall function example and also why the equation of both terms are different,

thanks
zahid

yousefaz August 2, 2017 00:01

When defining a wall function UDF in Fluent, the user is required to specify equations for the dimensionless velocities U* and its derivatives with respect to dimensionless distance away from the wall (y* or y+).

Hence, DUPLUS is the first derivative: dU*/dy+ and D2UPLUS is the second derivative d2U*/d(y+)2.

m zahid August 2, 2017 02:24

Quote:

Originally Posted by yousefaz (Post 659193)
When defining a wall function UDF in Fluent, the user is required to specify equations for the dimensionless velocities U* and its derivatives with respect to dimensionless distance away from the wall (y* or y+).

Hence, DUPLUS is the first derivative: dU*/dy+ and D2UPLUS is the second derivative d2U*/d(y+)2.

thanks yousefaz

sbaffini August 3, 2017 07:45

Quote:

Originally Posted by yousefaz (Post 659193)
When defining a wall function UDF in Fluent, the user is required to specify equations for the dimensionless velocities U* and its derivatives with respect to dimensionless distance away from the wall (y* or y+).

Hence, DUPLUS is the first derivative: dU*/dy+ and D2UPLUS is the second derivative d2U*/d(y+)2.


That's basically true.

You might want to give a look at this for more details:

https://www.politesi.polimi.it/bitst...Monticelli.pdf


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