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icoFoam - Floating point exception (core dumped)
Hi to everyone,
I have a problem with running a icoFoam on my own mesh. It is a simple model with one inlet and one outlet. The intention is to make a pressure driven flow as I use a very small mesh 1.4x1.4x1.4 mm pressure difference is 5 Pa Most of the files are copied from icoFoam tutorial case (cavity) of course I adopted them to my case. Mesh is generated in Avizo and then imported to enGrid and from there to openFoam. I must point that the same mesh works in Fluent without any problem. Case loads all the input files and starts the caluculation but after the first step it brakes. Here is the log. PHP Code:
0: https://dl.dropboxusercontent.com/u/122319307/0.tar.gz constant: https://dl.dropboxusercontent.com/u/...onstant.tar.gz system: https://dl.dropboxusercontent.com/u/.../system.tar.gz Also I runned checkMesh and I had some warning which I don't know how to fix so here is the output: PHP Code:
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I have no idea why your case fails, don't have time or much experience to check; what I do know is that you should take into account that your Knudsen is of the order of unity and you may have significant deviation from reality. If this is your final project and not a toy problem, you could/should try dsmcFoam, if you have time and patience.
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Hello Filip,
ich could reproduce your error. I don't know how you can get rid of the checkMesh Error - I never used the softwares you used. But I think the error is similar to the one discussed here (although it is a diffenrent solver) http://www.cfd-online.com/Forums/ope...mbit-mesh.html Maybe you can try this analogously in icoFoam? Maybe it is also a problem in the pEqn? In your case it might derive from the error in the mesh.. regards Nicklas |
Thank you Nicklas,
I made some tests and it definitely seems like the problem is with mesh, also in my solver there isn't the part which you commented out of the solver that you used. Nevertheless thank you very much for taking time and looking at my case Regards Filip |
So I finally solved this problem, there were several things to solve.
First the mesh was bad so when you run check mesh this shouldn't appear *Number of regions: 4 The mesh has multiple regions which are not connected by any face. <<Writing region information to "0/cellToRegion" and regarding the problem with high Courant number that occurred after solving mesh problems I referd to this thread and solved everything http://www.cfd-online.com/Forums/ope...-explodes.html Filip |
1 Attachment(s)
Hello :)
I have the same problem :( but your last suggestion is not working in my case. I am still in the learning phase and want to learn a lot about OpenFOAM. I try to simulate a laminar flow around around a semi-cylinder. The mesh was built using Fluent and the solver is icoFoam and i added the temperature in the solver. here is the link, that i followed : http://openfoamwiki.net/index.php/Ho...ure_to_icoFoam the time step is 0.0003 s (i would like to use 0.003 s) the U-inlet is 0.36 m/s. My Problem is, that icofoam is not stable and crash after 0.0054 s. Output: Code:
Time = 0.0051Output: Code:
Time = 0.36I could not upload all the files , the size of constant folds exceed the limitation. thx for support :) |
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your courant number is too high..
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as you are relatively new to Open foam. @Amin, i suggest you start learning it by doing the tutorials. example start with cavity and then proceed with elbow.
Then after doing those tutorials you can proceed with others example the ones with pisoFoam and simpleFoam... gradually you will get the hang of it. Then in case when you do your semi cylinder and stil have problem then i will sent you mine. I have already done one same in the past.. Good luck zaynah |
Hi Amin, there are multiple reasons for such a high Courant number, and it causes OpenFoam to brake. Please provide whole case and then somebody could help you
Good luck Filip |
Hello :)
Thx Thx Thx Thx Thx for your answer :) your courant number is too high... i know :( I am new in the world of OpenFoam, but did already the basic tutorials like ( cavity and airFoil2D...) and learned how to use blockMesh and built my own mesh and geometry :D I built the mesh of this case using fluent, but i do not know, how to stabilize the solver :confused: |
did you convert your fluent mesh to foam corectly? did you do a checkMesh? Did you check whether your velocoty lies in the laminar regime?
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yes :)
here is the output : Code:
Create time |
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Just decrees your time step. I put 0.00003 in your case and it seems to work like a charm ;)
I've read that you want to have time step 0.003 but this is simply impossible or I do not know how to do it P.S not to forget I solved it without temperature, at the moment I don't have time and volition to do that |
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1- you can use pisoFoam or simpleFoam for laminar flow too 2- use adjustTimeStep and limit courant number less than one, if you are using timeStep, then you need to choose your time step carefully 3- if you have problem, in temperature stability, please run your case with out solving for energy :), let flow get steady state, then apply your energy equation P.S. i did not look your case, and these are general suggestion ;) |
i check your case, i almost sure problem returns your mesh ;), first try a coarse mesh to see weather you reach an stable result or not
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the mesh around the geometry is very fine to capture the the boundary layer.
I tried to run the simulation with coarse mes, ant it is working fine. However i need to use the mesh, which i uploaded (fine mesh)..... So i shouldnot change the mesh. I tired to use dt=0.00001s the simulation is working, but it will take a lot of time to reach the 100 s. I think using the timestep is not the ideal idea for this case. ....:confused: |
if you want a final steady-state solution, why dont u use simpleFoam?
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