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October 19, 2018, 03:53 |
Drag calculation for porous zone
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#1 |
Member
Anders Dyhr Nørløv
Join Date: Aug 2018
Posts: 32
Rep Power: 8 |
Hello
I've tried to implement the following script, for a plate placed in a free flowing air. And calculated the drag coefficient on the square. This works really well. (The squareVolume reffers to the boundary around the square). Now I would like to do the same, but where I have replaced the square with a porous region. Now I don't have the boundary to put into my script. I tried putting the volume of the porous region into the script but that does not work, and I get a value of zero. I also tried creating a boundary around the porous region, however, then the boundary affects the simulation, and I could still not calculate the drag force. Any idea how i could get the drag force on my porous region? I've included a image of my simulation of the porous region. Clearly there should be a drag force on it. Udklip.PNG Code:
forces { type forces; functionObjectLibs ("libforces.so"); outputControl timeStep; outputInterval 1; patches ( "squareVolume" ); p p; U U; rho rhoInf; log true; CofR (0.25 0 0); rhoInf 1; } forceCoeffs { type forceCoeffs; functionObjectLibs ( "libforces.so" ); outputControl timeStep; outputInterval 1; patches ( "squareVolume" ); p p; U U; rho rhoInf; log true; liftDir (0 0 1); dragDir (1 0 0); CofR (0.25 0 0); pitchAxis (0 1 0); magUInf 5.00; rhoInf 1; lRef 1; Aref 0.25; } |
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October 26, 2018, 05:06 |
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#2 |
Member
Anna Feichtner
Join Date: Dec 2016
Location: Cornwall (UK)
Posts: 36
Rep Power: 9 |
Hi Anders,
I would be interested in something simlar... I have not tried it yet, but I was thinking about applying internal baffles (createBaffles with type "cyclic"). I guess I would have tried something like: - createBaffles (type cyclic) out of faceSets/faceZones - then I'd have 4 internal patches surrounding the porous are that are "empty" - somehow link them together? to get one external surface... - use this surface as input patch for the forces functionObject However, that's just an idea... Please keep me updated about any progress Best wishes, Anna |
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February 8, 2019, 13:27 |
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#3 | |
Senior Member
Join Date: Jun 2011
Posts: 163
Rep Power: 15 |
Quote:
Dear MrAndersDk I have the same problem can you find a way for calculating this force ? Best Regards |
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February 11, 2019, 04:10 |
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#4 |
Member
Anders Dyhr Nørløv
Join Date: Aug 2018
Posts: 32
Rep Power: 8 |
Hello
Been some time since I looked at it, but I think I solved it. I will post my case files later when I'm at my work compete, maybe first tomorrow. |
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February 11, 2019, 05:17 |
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#5 |
Member
Anders Dyhr Nørløv
Join Date: Aug 2018
Posts: 32
Rep Power: 8 |
Hello
Been some time since I looked at it, but I think I solved it. I will post my case files later when I'm at my work compete, maybe first tomorrow. |
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February 12, 2019, 11:53 |
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#6 |
Senior Member
Join Date: Jun 2011
Posts: 163
Rep Power: 15 |
Hello
Dear MrAndersDk thanks for your kindness |
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February 13, 2019, 06:56 |
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#7 |
Member
Anders Dyhr Nørløv
Join Date: Aug 2018
Posts: 32
Rep Power: 8 |
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February 13, 2019, 10:05 |
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#8 |
Senior Member
Join Date: Jun 2011
Posts: 163
Rep Power: 15 |
Hello
Dear MrAndersDk thanks again for your kindness can you explain this case and its setting its polyMesh folder is empty. moreover, how you solved the aforementioned problem ? Best Regards |
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February 13, 2019, 11:21 |
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#9 |
Member
Anders Dyhr Nørløv
Join Date: Aug 2018
Posts: 32
Rep Power: 8 |
The polymesh folder was too big for uploading. I'm away on a business trip, but when I get back I will have a look at it.
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February 14, 2019, 02:54 |
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#10 |
Member
Anders Dyhr Nørløv
Join Date: Aug 2018
Posts: 32
Rep Power: 8 |
Hello
Now I'm back. Look in the forceCoeffs file in the system folder. The solution is to include the porosity true line, and then the patch i put in my volume that has porosity. The forceCoeffs file is then included in the controlDict. |
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February 14, 2019, 16:15 |
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#11 |
Senior Member
Join Date: Jun 2011
Posts: 163
Rep Power: 15 |
Hello
Dear MrAndersDk thanks again for your kindness Best Regards |
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February 28, 2019, 08:37 |
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#12 |
Member
Anna Feichtner
Join Date: Dec 2016
Location: Cornwall (UK)
Posts: 36
Rep Power: 9 |
Hey MrAndersDk
Thanks for sharing your case files. I was just wondering, if the force and forceCoeffs calculation really worked as your attached .dat files in the postProcessing folder show only zeros? And I have encountered problems with the forces functionObject utility for my current case, which is a 2D water wave interaction problem with a thin porous sheet (using interFoam/olaFlow). The forces utility gave me weird results, so I have used the pressureDifferencePatch utility instead, which gives reasonable results. I would have thought it would give the same results, but it didn't and I still can't find the reason. Also the forces utility somehow cannot access my total(p) field, it only works for the p field for me... Anna |
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February 28, 2019, 08:41 |
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#13 |
Member
Anna Feichtner
Join Date: Dec 2016
Location: Cornwall (UK)
Posts: 36
Rep Power: 9 |
Oh sorry, I have opened the wrong files... So it was working!
And you are confident that the forces/forceCoeffs utility gives the right solution? Best wishes Anna |
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February 28, 2019, 08:47 |
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#14 |
Member
Anders Dyhr Nørløv
Join Date: Aug 2018
Posts: 32
Rep Power: 8 |
I have not verified the results. All I can say is that for my purpose the results makes sense. And others has made independent simulations in other programs and agree with my results.
But it is not well tested |
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February 28, 2019, 08:55 |
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#15 |
Member
Anna Feichtner
Join Date: Dec 2016
Location: Cornwall (UK)
Posts: 36
Rep Power: 9 |
Alright, sounds reasonable. Thank you!
Anna |
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January 8, 2024, 10:52 |
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#16 | |
New Member
Kazakis Ioannis
Join Date: Sep 2016
Location: Thessaloniki, Greece
Posts: 24
Rep Power: 9 |
Quote:
Dear sir How you connect porous media with patch?? patch also nedds boundary conditions! Kind Regards Yiannis |
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