# beginner in adaptive mesh refinement

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 July 8, 2010, 10:57 beginner in adaptive mesh refinement #1 New Member   yafuji aki Join Date: Jul 2010 Location: Japan Posts: 14 Rep Power: 8 Hi to everyone! I am Aki, a beginner in OpenFOAM. I am intrested in adaptive mesh refinement and I managed to find "dynamicMeshDict" dictionary, but I am not sure how it works... Would you tell me a condition of the refinement? The mesh is refined automatically when the velocity (or the Courant number) exceeds a given value? And, I am not sure coefficients in the dictionary... constant/dynamicMeshDict -------------------------------------- dynamicFvMesh dynamicRefineFvMesh; dynamicRefineFvMeshCoeffs { refineInterval 1; field alpha1; lowerRefineLevel 0.001; upperRefineLevel 0.999; unrefineLevel 10; nBufferLayers 1; maxRefinement 2; maxCells 200000; correctFluxes ( ( phi U ) ); dumpLevel true; } -------------------------------------- I have performed some tutorials, so I guess "maxRefinement" means the max refinement number. But I cound only understand it. I can not understand what "refineInterval" and "maxCells" mean. And what are "lowerRefineLevel" and "upperRefineLevel"...? I would be grateful if you could provide me the meanings of them. Thanks in advance! Aki

 July 9, 2010, 04:47 #2 Member   Join Date: May 2009 Posts: 31 Rep Power: 9 As far as I understand: refineInterval - specifies how often (every n:th timestep) the grid should be refined. maxCells - limits the number of cells, should never be greater than the given number, an approximate number. lowerRefineLevel - grid gets refined if "alpha1" is lower than this value. upperRefineLevel - grid gets refined if "alpha1" is bigger than this value. mm.abdollahzadeh and ArathoN like this.

 July 9, 2010, 13:39 #3 New Member   yafuji aki Join Date: Jul 2010 Location: Japan Posts: 14 Rep Power: 8 Dear KrisT Thank you very much for your help! I have performed some tutorials by changing them. May I ask one more question??? What is "correctFluxes" ? These values are corrected each time step? Aki

July 9, 2010, 14:20
#4
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Join Date: May 2009
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Rep Power: 9
Quote:
 Originally Posted by aki_yafuji Dear KrisT Thank you very much for your help! I have performed some tutorials by changing them. May I ask one more question??? What is "correctFluxes" ? These values are corrected each time step? Aki
Not sure about this one. Something about fluxes to correct when refining (phi), and variable they can be ineterpolated from (U).

 March 27, 2012, 07:06 #5 Member   Join Date: Aug 2011 Posts: 83 Rep Power: 7 Hello, I looked into the code and find following: nBufferLayer: Number of layers between different refinement levels I understand it in that way: nBufferLayer 1 means: a cell, which was refined once, can only be a neighbour of a cell which is not refined or refined twice. But this cell canīt be a neighbour of a cell which is refined three times. In a tutorial I found the definitoin for maxRefinement: maxRefinement means the number of refinements that are allowed for one cell. But does everybody know what "unrefineLevel" mean? Thanks a lot Last edited by idefix; April 3, 2012 at 02:39.

 May 23, 2012, 11:17 #6 Member   Join Date: Aug 2011 Posts: 83 Rep Power: 7 has nobody an idea what it could mean? I would be really happy to get some help

 February 29, 2016, 03:59 Vortex Refinement #7 Member   Peter Join Date: Nov 2015 Location: Hamburg, Germany Posts: 31 Rep Power: 2 Dear Foamers, I have another question concerning the settings in the dynamicMeshDict-file. I would like to refine a tip vortex dynamically, so with the pimpleDyMFoam-solver. As entry 'field' in dynamicMeshDict I would like to use something like Lambda2. How can I tell the solver to calc this field?

 August 1, 2016, 09:08 #8 Member   Peter Join Date: Nov 2015 Location: Hamburg, Germany Posts: 31 Rep Power: 2 Finally, I programmed a new solver based on pimpleDyMFoam. There, I calculated the nedded scalar field (like Lambda2). In constant/dynamicMeshDict I specify the variables that prescribe the refinement and so it works afrotimy likes this.

August 28, 2016, 22:20
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Francis
Join Date: Jan 2014
Location: Toronto
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Quote:
 Originally Posted by potentialFoam Finally, I programmed a new solver based on pimpleDyMFoam. There, I calculated the nedded scalar field (like Lambda2). In constant/dynamicMeshDict I specify the variables that prescribe the refinement and so it works
Hi Peter,

Is this new solver working with dynamicRefineFvMesh in 2D ?

 August 29, 2016, 03:03 #10 Member   Peter Join Date: Nov 2015 Location: Hamburg, Germany Posts: 31 Rep Power: 2 Hi Francis, what do you mean with 'dynamicRefineFvMesh'? I didn't try but I think it should work in 2D - why not? Regards, Peter

 August 29, 2016, 06:54 #11 Member   OpenCFD Join Date: Mar 2009 Posts: 47 Rep Power: 9 The dynamic refinement is cutting cells 2x2x2 - in all directions, so you would create mesh cells in directions you are not solving for. Which would be not such a problem, but you are creating also non-orthogonality and you will have parasitic fluxes in the direction you are not solving for and your solution is loosing precision at least.

 August 29, 2016, 06:57 #12 Member   Peter Join Date: Nov 2015 Location: Hamburg, Germany Posts: 31 Rep Power: 2 Thanks! That's correct. So it works, but not in the desired way.

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