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

Before compiling the UDF in Fluent you need to start Fluent in a C++ DOS window.

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]

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]

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]

Originally Posted by yousefaz

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]

Originally Posted by yousefaz

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