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June 21, 2010, 16:00 |
New to OpenFOAM
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#1 |
Member
Scott
Join Date: Sep 2009
Posts: 30
Rep Power: 16 |
Hello,
I am just getting started with openFOAM and have found the learning curve to be pretty steep. I am able to generate meshes of my flow volumes and export them as a .UNV (Ideas) format from UG/NX. Its very easy to specify the flow conditions in NX (i.e. velocity, altitude, materials, etc.) I'm not clear on how to do it in openFOAM. It looks like all this would be done in the controlDict file. Also in the tutorials I have seen reference to specifying which patches make up the boundaries, do I have to specify these patches manually? What if I have 1,000,000 elements and thousands of patches on a boundary face? Do I have to manually specify them all? Where do I specify my initial conditions, flow velocity, pressure, material (Air)? Can I measure lift and drag of a protrusion in the flow volume? I suppose this stuff is all in the user guide but it isn't really clear on where it is. I have read through it but still have tons of questions. If anyone can help I would really appreciate it. Thanks Scott |
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June 22, 2010, 02:17 |
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#2 |
Senior Member
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,912
Rep Power: 36 |
Please, read the manual again, go through the tutorials. Many of the questions you asked will find an answer if you go through the tutorials in the User's guide and in the Programmer's guide.
I would suggest you follow the tutorials step by step, and then, if you have questions feel free to ask again. One suggestion: use one independent thread for each question, and, before opening a thread, use the search function of the forum. Many answers are already there. You can find also some more information on the wiki: http://openfoamwiki.net/ Thanks
__________________
Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541) OpenQBMM - An open-source implementation of quadrature-based moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using. |
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June 23, 2010, 19:57 |
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#3 |
Senior Member
Daniel WEI (老魏)
Join Date: Mar 2009
Location: Beijing, China
Posts: 689
Blog Entries: 9
Rep Power: 21 |
Alberto, you are so kind. I found your name every place where people need help.
Your answers are always characterized with Clarity, Well-Organization, and Practical Guidance. They are so helpful.
__________________
~ Daniel WEI ------------- Boeing Research & Technology - China Beijing, China |
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June 24, 2010, 00:09 |
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#4 |
Member
Join Date: Jun 2010
Posts: 33
Rep Power: 15 |
I just started running my very first OpenFOAM case. And unlike other CFD programs, OpenFOAM doesnt really give a visual representation of whats going on. So I was just wondering if anyone could help me out in figuring out whether the code is going in the right direction.
Code:
DILUPBiCG: Solving for epsilon, Initial residual = 1.95207e-06, Final residual = 1.95207e-06, No Iterations 0 DILUPBiCG: Solving for k, Initial residual = 7.29185e-06, Final residual = 7.29185e-06, No Iterations 0 DILUPBiCG: Solving for Ux, Initial residual = 2.08313e-10, Final residual = 2.08313e-10, No Iterations 0 DILUPBiCG: Solving for Uy, Initial residual = 2.29687e-10, Final residual = 2.29687e-10, No Iterations 0 DILUPBiCG: Solving for Uz, Initial residual = 4.2889e-08, Final residual = 4.2889e-08, No Iterations 0 DILUPBiCG: Solving for h, Initial residual = 5.49913e-06, Final residual = 5.49913e-06, No Iterations 0 DICPCG: Solving for p, Initial residual = 4.64395e-05, Final residual = 5.84329e-14, No Iterations 1 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 time step continuity errors : sum local = 7.35752e-05, global = 5.5069e-05, cumulative = 2.00842 rho max/min : 16.4971 0.00201364 bounding p, min: 306.907 max: 1.34522e+06 average: 106238 Cheers! T |
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June 24, 2010, 00:57 |
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#5 |
Senior Member
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,912
Rep Power: 36 |
OF shows you the residuals of each equation and some other information (bound variables, conservation information, ...).
If you want, you can plot residuals in real time with pyFoamPlotRunner, which is part of pyFoam http://openfoamwiki.net/index.php/Contrib_PyFoam Best,
__________________
Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541) OpenQBMM - An open-source implementation of quadrature-based moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using. |
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June 24, 2010, 01:03 |
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#6 |
Member
Join Date: Jun 2010
Posts: 33
Rep Power: 15 |
Hey Alberto!
Thanks for your shifty response! I will give pyFoam a shot soon. But as of today, the senior engineer isnt here and Im unable to work with him with pyFoam. So I was just wondering if you could let me know whether it seems like the calculations are running correctly? If it is, then Im going to let it run through the night. If its not, then I can wait till tomorrow! Cheers, T |
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June 24, 2010, 11:09 |
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#7 | |
Senior Member
Daniel WEI (老魏)
Join Date: Mar 2009
Location: Beijing, China
Posts: 689
Blog Entries: 9
Rep Power: 21 |
Quote:
__________________
~ Daniel WEI ------------- Boeing Research & Technology - China Beijing, China Last edited by lakeat; June 24, 2010 at 11:33. |
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June 24, 2010, 12:05 |
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#8 | |
Senior Member
Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
Posts: 1,912
Rep Power: 36 |
Quote:
About knowing if the simulation is correct or not, well the code is running, and the equations are not diverging, even if some variable is bounded (normal in unsteady runs). I would suggest to save the output in a log and look at the evolution of the initial residuals (you can plot them with pyFoamPlotWatcher.py too) after, when your supervisor is there. In addition, as Daniel said, you've to check the results and the setup. Residuals are just a part of the story. Best, A.
__________________
Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541) OpenQBMM - An open-source implementation of quadrature-based moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using. |
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June 26, 2010, 09:04 |
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#9 |
Senior Member
Jiang
Join Date: Oct 2009
Location: Japan
Posts: 186
Rep Power: 16 |
Dear Lakeat and Alberto,
Do you have used "directMapped" boundary in tutorials/incompressible/pisoFoam/les/pitzDailyDirectMapped . I have tried the "nearestCell" ,it works fine, but the method "nearestFace" doesn't work for me . I can't find the reason ,and my work can not be going on. Seldom people can give me common, do you have some suggestions ? http://www.cfd-online.com/Forums/ope...ng-method.html I am sorry to disturb this thread, but I must come here to fine you. |
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