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[blockMesh] Where can we find more details about blockMesh's algoritms? |
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November 3, 2015, 02:07 |
Where can we find more details about blockMesh's algoritms?
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#1 |
Senior Member
Join Date: Sep 2015
Location: Singapore
Posts: 102
Rep Power: 10 |
Dear Santos,
Thanks for the page on blockMesh. You have introduced me to the world of m4 programming. ;-) I have a question for you: what is the algorithm used by blockMesh? I am trying to mesh a varying cross-section nozzle and the current code does not perform well when I use a spline along the length. I found out that it is long standing problem in blockMesh. So, I want to try to correct it but I am lost at the code found in 'blockCreate.C'. It uses weights, importance factors, correction vectors, etc. I do not quite understand it. Do you know of any source (website/paper) that describes the principles behind blockMesh? Once again, many thanks! |
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November 7, 2015, 12:16 |
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#2 |
Retired Super Moderator
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 10,975
Blog Entries: 45
Rep Power: 128 |
@usv001 - Quick answer: I'm not aware of any document that explains how do the internal systems work in blockMesh. But the code is open source and it should be just a matter of inspecting the source code.
If you feel that this is really a bug, then open a bug report on the bug tracker, but please provide more details for the problem itself. If you offer to help with fixing this issue, Henry might be able to provide you with some description of the current limitation that algorithm has got... at least beyond the ones that are already described on the bug tracker. You can find several if you Google: Code:
site:openfoam.org/mantisbt blockMesh |
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November 9, 2015, 06:35 |
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#3 |
Senior Member
Join Date: Sep 2015
Location: Singapore
Posts: 102
Rep Power: 10 |
Dear Santos,
Once again, thanks for the reply. Here is what I have done up to now: I tried to mesh a nozzle of varying cross-section. The current blockMesh algorithm does not scale/propagate the arcs properly along the length of the nozzle. You can see the pictures attached (mesh_before_correction_1 & 2). It is the same bug that was raised earlier. I tried using the patch provided by Henry (Thanks to Henry!). It seems much better now (mesh_after_correction_1 & 2). But I want to make sure that it really does what it looks like it's doing - that is, it really scales the arc properly. Earlier I have been trying to mesh just a quarter of the nozzle and using mirrorMesh to obtain the full nozzle. The fix by Henry does not seem to work for that case. - - - I have gone through the code in blockCreate.C. I understand that the process starts with identifying the a point on each of the 12 edges which corresponds to the (i,j,k) of the internal point we would like to find. But after that, I am not sure what exactly happens with importance factors, correction vectors, etc. Thanks for all the help! |
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November 15, 2015, 15:36 |
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#4 | |
Retired Super Moderator
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 10,975
Blog Entries: 45
Rep Power: 128 |
Quick answers:
You might want to double-check who posted what in the "Issue History" section of the bug report: http://www.openfoam.org/mantisbt/vie...d=1396#history Quote:
Code:
Info << "k:" << k << " -> corz4: " << corz4 << endl; Such an example already exists in OpenFOAM... let me see if I can find the thread... ah the utility is datToFoam and the thread is this one: http://www.cfd-online.com/Forums/ope...rmat-help.html |
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November 17, 2015, 07:45 |
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#5 |
Senior Member
Karl-Johan Nogenmyr
Join Date: Mar 2009
Location: Linköping
Posts: 279
Rep Power: 21 |
This might be an alternative:
http://www.cfd-online.com/Forums/ope...blockmesh.html Or look at extBlockMesh as discussed in the bug report. extBlockMesh may not handle grading, though. |
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