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-   -   5 questions about UDF usage?????? (http://www.cfd-online.com/Forums/fluent/41810-5-questions-about-udf-usage.html)

Asghari July 21, 2006 07:31

5 questions about UDF usage??????
 
Hi all;

I have some questuin from you about udf's:

1- Are C_T(cell,cell_thread) , C_P(cell,cell_thread) macros, which one ,static or absolute temperature and pressure,respectively?

2-In the two phase flows , if i use from Define_source for computing the source term of vof equation at primary phase and i solve this equation , how to calculate fluent vof of secondary phase ? is it neccessary to solve vof of secondary phase ?

3-Why is C_UDMI(c,t,x) macro use instead of C_udsi(c,t) ?

4-While i am using Define_source macro, I want no effect on other equations.How would it possible?

5-3-Why is Reconstruction gradients use instead of gradients?

can answer everybody to one of this questions,Please?

Thanx in advance.

jasond July 21, 2006 12:31

Re: 5 questions about UDF usage??????
 
I can answer some of your questions:

> 3 - Why is C_UDMI(c,t,x) macro use instead of C_udsi(c,t) ?

C_UDMI is used for user-defined memory and C_UDSI is used for user-defined scalars. For scalars you generally have Fluent solve a transport equation while for the scalar, while for user-defined memory you are in charge of making it mean anything.

> 4 - While i am using Define_source macro, I want no effect on other equations.How would it possible?

If I understand what you mean, this should be taken care of when it is hooked into Fluent. Maybe I don't understand you.

> 5 - Why is Reconstruction gradients use instead of gradients?

According to the documentation, using the reconstruction gradients will give values more in line with surrounding cells. However, I asked Fluent about this and was told that I didn't need to use them for my application (interpolation within cell).

Jason

Asghari July 24, 2006 01:08

Re: 5 questions about UDF usage??????
 
Ok,I have also three other questions from you. Please help me.

6-While we are looping on cells in a cell thread, Are successive cells in loop same neighboring cells,certainly ?

7-How to compute diffusivity of a variable in faces (not cells) ?

8-What are Storage variables(S_phi)?

jasond July 24, 2006 15:51

Re: 5 questions about UDF usage??????
 
I can answer 2 of your questions:

6) No, I don't think you can make that sort of assumption. That would be grid dependent.

7) I don't know how off hand, but I would look at how Fluent does this sort of thing (I think it would need to do something similar for turbulence models. Could be wrong, though).

8) Can't help with this one.

Jason

asghari July 26, 2006 05:59

Re: 5 questions about UDF usage??????
 
Thank you;

I want information about following macro,urgently:

Boundary_Secondary_gradient_Source

Do you have information from this macro and argument type ?

How can i access to this informations?

Please help me ;

Thank alot.

Asghari

jasond July 27, 2006 09:46

Re: 5 questions about UDF usage??????
 
Well, I have never used it myself, so I can't give any firsthand info to you. However, the UDF manual does have some information and an example (I just looked) - so I would look at that. I do know that you have to call BOUNDARY_FACE_GEOMETRY to get some geometry stuff before you can use the macro you speak of.

Jason

P.S. Google might also help...


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