zero-diffusion (constant gradient) boundary condition

thomas99 · July 26, 2011, 09:39

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, 19:01

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, 05:53

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, 08:35

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

thomas99 · July 29, 2011, 05:59

Thanks akidess, that's what I was looking for

July 26, 2011, 09:39	zero-diffusion (constant gradient) boundary condition	#1
thomas99 New Member Tom Witten Join Date: May 2011 Location: Freiberg Posts: 10 Rep Power: 15	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

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July 26, 2011, 19:01		#2
Cyp Senior Member Cyprien Join Date: Feb 2010 Location: Stanford University Posts: 299 Rep Power: 18	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

July 27, 2011, 05:53		#3
thomas99 New Member Tom Witten Join Date: May 2011 Location: Freiberg Posts: 10 Rep Power: 15	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

July 27, 2011, 08:35		#4
akidess Senior Member Anton Kidess Join Date: May 2009 Location: Germany Posts: 1,377 Rep Power: 30	Thomas, have a look at this thread: http://www.cfd-online.com/Forums/ope...condition.html

July 29, 2011, 05:59		#5
thomas99 New Member Tom Witten Join Date: May 2011 Location: Freiberg Posts: 10 Rep Power: 15	Thanks akidess, that's what I was looking for