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-   -   UDS formulation for axisymmetric domains URGENT (http://www.cfd-online.com/Forums/fluent/47837-uds-formulation-axisymmetric-domains-urgent.html)

Sandilya Garimella April 7, 2008 14:05

UDS formulation for axisymmetric domains URGENT
 
Hello All

I am trying to solve for UDS in Fluetn with an Axisymmetric model

But the UDS theory is given for 2D models but not for axisymmetric models

I am not sure what to do!!!

Should I write UDF for a 2D domain using theory given in Fluent Manual and incorporate the same into my axi-symmetric model

Please let me know

Thank you.

Regards Sandilya

Aris Nikolopoulos April 8, 2008 03:15

Re: UDS formulation for axisymmetric domains URGEN
 
Yes, it's the same!

There are some minor differences though in axisymetric! Not in UDS but in all UDFs.

For example be carefull with some functions (C_VOLLUME) because sometimes multiply their output with (2*PI)

Sandilya Garimella April 10, 2008 09:19

Re: UDS formulation for axisymmetric domains URGEN
 
thank you very.

The reason for my question is that i am solving for electric potential and charge transport in bulk gas flow

In a 2d model the equations converge

But in Axisymmetric setting, the charge transport equation diverges immediately

I am not able to understand the reason

Rami April 14, 2008 04:32

Re: UDS formulation for axisymmetric domains URGEN
 
You should look at the UDS as a tensor scalar transport equation. Then, you can explicitly write it in ANY coordinate system (including 2D Cartesian, axisymmetric etc). All you need is to know how the tensor terms, like covariant derivatives, are presented in your system. For axisymmetric cylidrical system, you may find these equations in most texbooks, and maybe even in Fluent documentation.


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