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-   -   zero-diffusion (constant gradient) boundary condition (http://www.cfd-online.com/Forums/openfoam/90947-zero-diffusion-constant-gradient-boundary-condition.html)

thomas99 July 26, 2011 08:39

zero-diffusion (constant gradient) boundary condition
 
Hi all,

I'm still relatively new to openfoam and despite searching through the tutorials, source code, and this forum have not been able to determine if the zero-diffusion boundary condition is available in openfoam or easily implemented.

Has anyone used this type of boundary condition in openfoam before?

Cheers,
Tom

Cyp July 26, 2011 18:01

Hi Tom, and welcome on board!

I believe that the BC you are looking for is zeroGradient. You just have to write " type zeroGradient;" within our patch.

@++
Cyp

thomas99 July 27, 2011 04:53

Hi Cyp,

Thanks for the reply! What I'm looking for though is the zero-diffusion outlet boundary condition, not the zero-gradient boundary condition.

A zero-diffusion boundary condition is of the form d^2(phi)/d(n^2) = 0 where phi is a transported variable (e.g. a component of velocity, temperature, viscosity, ...). Typically when this condition is set at an outlet, the value of the node at a particular outlet position is calculated from the interior situated nodes as well as the first derivative which is some constant.

I think both fluent and cfx allow implementation of this boundary condition and wanted to know if openfoam also has this option as I would like to test openfoam for a few studies.

Cheers,
Tom

akidess July 27, 2011 07:35

Thomas, have a look at this thread: http://www.cfd-online.com/Forums/ope...condition.html

thomas99 July 29, 2011 04:59

Thanks akidess, that's what I was looking for


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