How to define wall velocity in Density-based solver using UDF

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Last Post 18 March 2019

amin1364 posted this 14 March 2019

Dear all,

I want to implement slip boundary condition using UDF in density-based solver. But the problem is, in the mentioned solver, we can not use F_U(f,t) macros. I am wondering whether it is possible to get access to that value or not?

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rwoolhou posted this 14 March 2019

Where does it say you can't use F_U(f,t) in the Density based solver? Why can't you just set the wall shear to zero in the GUI panel?

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amin1364 posted this 16 March 2019

Thanks for your prompt response

I found the argument in the following link address,

https://www.sharcnet.ca/Software/Fluent6/html/udf/node91.htm

in which it is stated as follows:

"The macros listed in Table 3.2.20- 3.2.23 can be used to return real face variables in SI units. They are identified by the F_ prefix. Note that these variables are available only in the pressure-based solver. In addition, quantities that are returned are available only if the corresponding physical model is active. For example, species mass fraction is available only if species transport has been enabled in the Species Model dialog box in ANSYS FLUENT. Definitions for these macros can be found in the referenced header files (e.g., mem.h)"

and the reason that I can't set the wall shear to zero in the GUI is that I need to implement Maxwell slip and after that temperature jump is required to be added. Moreover, I am totally aware of existence of such B.C. in fluent for low pressure but I have to use Density-based solver.

As you may know in this B.C. knowing the value of wall velocity (or temperature for temperature jump B.C.) on wall itself and fist cell adjacent to the wall is vital.

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rwoolhou posted this 18 March 2019

Thanks, found it in the current DOC too: in R19 you can access the correct documentation rather than the v6 version in Sharcnet (v6 was released about 17 years ago). Reading through the rest of the current DOC suggests the values aren't stored as the coupled nature of the solver means they're used & immediately discarded.

I can't help here: it's outside of our working rules (courtesy of ANSYS legal & export law) and I can't get our second line teams involved (same reason). However, if your supervisor gets in touch with the local office we (ANSYS worldwide or local resellers) may well be able to assist.