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Atit Koonsrisuk February 16, 2005 14:42

Pressure as the variable in Expression in CFX-Pre
Please someone suggest me how to use 'Pressure' and 'area' at a certain face inside the domain as the variable in 'Expressions' of CFX-Pre.

I would like to define one variable in 'Expressions' of CFX-Pre as the function of the pressure at one certain face of my domain. I found the name of face is F5.B1.P3 and the formula is the pressure at that face times face area. However I do not know how to define that pressure. I already tried:

Pressure@F5.B1.P3 and Pressure()@F5.B1.P3 and Pressure("F5.B1.P3") and massFlowAve(Pressure)@F5.B1.P3

but none of them is acceptable. Do anyone know how to define the pressure at certain face in 'Expressions'

In addition, Function Calculator in CFX-Post can compute 'area' at any face, so there must be 'area' as the parameter in CFX, isn't it? However I have no idea how to get 'area' to use in CFX-Pre. I have tried:

area@F5.B1.P3 and area()@F5.B1.P3

they all doesn't work. In my domain, there are some 2D regions that I specify the boundary conditions. For example, I have 'in' as the 2D region for 'Inlet' boundary condition. I have tried


CFX accept this definition, but the preprocessor does not support its evaluation in CFX-Pre. Do I have to define F5.B1.P3 as the 2D region? I think that we define 2D region for specifying boundary conditions, while this face is the face on fluid subdomain for energy source, which need not any boundary condition. So I think specify it as 2D region is not right, isn't it?

Thank you very much for your kind consideration.


Juan Carlos February 16, 2005 14:55

Re: Pressure as the variable in Expression in CFX-

The callback functions within CFX-Pre and the CFX-Solver only support the use of regions that are defined as : domain, sub-domain, boundary, domain interfaces, point sources or monitor points. There is no mechanism for accessing a face that is not a boundary or a domain interface.

Can you make that region a domain interface? and treat the subdomain as a domain?

For further information, you can look at the CEL Variables, Functions and Constants section of the CFX-5.7/5.7.1 documentation.

Regards, Juan Carlos

Atit Koonsrisuk February 16, 2005 15:09

Re: Pressure as the variable in Expression in CFX-
Dear Carlos, Thank you very much for your kind answer.

I follow your suggestion by defining that face as the domain interface named 'ADin'. As I stated earlier that


do work, but


doesn't work. Why?

In addition, do you have idea how to use pressure, because even


doesn't work

Thank you very much.


Juan Carlos February 16, 2005 16:18

Re: Pressure as the variable in Expression in CFX-

When you refer to the domain interface, you should refer to a side of it. Then, you really refer to the boundary on the side you are interest in. I think that will solve the area@ADin problem..

Second, callbacks are single value functions.. You cannot access the Pressure array on a boundary via a callback yet.. You can average, min, max the array but not access the array itself.. You may be confused with the syntax, for example area is a function not a variable with syntax area@location. Other example is areaAve(variable, like Pressure)@location.

For example, to obtain the area integral of Pressure over a surface, you do : areaInt(Pressure)@location

Regards, Juan Carlos

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