CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Programming & Development (http://www.cfd-online.com/Forums/openfoam-programming-development/)
-   -   Dirichlet–Neumann Partitioning BCs (http://www.cfd-online.com/Forums/openfoam-programming-development/116119-dirichlet-neumann-partitioning-bcs.html)

Giancarlo_IngChimico April 13, 2013 08:05

Dirichlet–Neumann Partitioning BCs
 
Hi all,
I have to implement the Dirichlet–Neumann Partitioning BCs for my solver that treats two different regions (fluid and solid).
Is there any preconfigured BC in the framework of OpenFoam?

Thanks

Regards

Giancarlo

ngj April 14, 2013 05:14

Hi Giancario,

I am not familiar with the term "Dirichlet-Neumann Partitioning", however, maybe the mixedFvPatch class is what you need.

In this class you can switch (smoothly) from a dirichlet to a neumann condition depending on the instantaneous dynamics of the system. I use it in the binary fashion to switch between fixed value and zero gradient, where the choice depends on the internal value of some concentration field.

Kind regards

Niels

Cyp April 14, 2013 15:45

Hi Giancarlo,

I fear there is no Direchlet-Neumann BC coded by default in OF and that you have to develop your owns. You can find a lot of informations in http://www.personal.psu.edu/dab143/O...ven_slides.pdf and its associated tutorial http://www.personal.psu.edu/dab143/O...erTraining.tgz.

The relaxation factors are quite important in this example.

@++
Cyp

Giancarlo_IngChimico April 14, 2013 17:20

Thanks a lot Cyp. This materials is fantastic. It's just what I was looking for.

Regards

Giancarlo

chriss85 May 30, 2014 08:48

In case you still read here, have you got this working?

I'm currently implementing something similar for electric potential between different regions.

By now OpenFOAM has a boundary condition for the temperature that uses an approach like this, called turbulentTemperatureCoupledBaffleMixed.

I adopted it to my needs, but I don't understand the weighting factor in the mixed formulation. Why is it set to this value? Does it help convergence if this value is used instead of some arbitrary value between 0 and 1 (like 0.5)?

Furthermore, how does relaxation help here? My current solver doesn't use relaxation (it's transient), and it requires quite some iterations initially until a consistent solution is reached (up to 30 in a test case I made).

The link mentioned using Aitken's delta˛ method (see here), which is basically a quadratic extrapolation of the convergence series of the field. In its current implementation, OpenFOAM doesn't use this. Have you implemented this? Is it worth it for transient cases? I believe that the convergence should be better in transient cases because the solution changes only a bit between steps.

chriss85 June 2, 2014 09:46

After some more investigation I figured out that relaxation didn't refer to the field relaxation, but rather to the coupling between the patches of different regions.

I also compiled the MRConjugateHeatFoam solver with OF2.3, but it doesn't calculate any sensible results and the solution of the example looks very incorrect. Has anyone tried this solver with success?

ahmmedshakil June 9, 2014 10:24

MRConjugateHeatFoam
 
Hi Chirss85,
I worked with the MRConjugateHeatFoam. In my case, I validated the solver with some experimental cases, and the results were really good. BTW, my problem was heat conduction between two solids (i.e. silicon on a glass substrates) due to laser annealing.

Cheers
shakil


Quote:

Originally Posted by chriss85 (Post 495215)
After some more investigation I figured out that relaxation didn't refer to the field relaxation, but rather to the coupling between the patches of different regions.

I also compiled the MRConjugateHeatFoam solver with OF2.3, but it doesn't calculate any sensible results and the solution of the example looks very incorrect. Has anyone tried this solver with success?



All times are GMT -4. The time now is 22:58.