similar problem, but maybe related to some BC
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Greetings all,
I know this is a very old thread but I'm facing a problem that looks very similar to the one posted here. I'm dealing with a multi region case with the chtMultiRegionFoam solver. My case is made up of some solid regions and a fluid region. It starts solving first the fluid region with no problem but when it starts to solve the first solid region the following error comes up: Code:
Solving for solid region fasana Code:
Cell determinant (wellposedness) : minimum: 0 average: 3.2312708 After I solved the problem with the under determined cells I ran the case again but the same error was shown, so I got stuck because I don't know what it really means and I don't know where to look up. I attach the changeDictionaryDict file and the T file belonging to the region that crashes so that you can check if there is something wrong in them. In case you need more files or even the entire case, just ask me for it! ;) Many thanks in advance. Regards, Alex |
Greetings Alex,
In a case like this, you should apply the good old strategy of "isolate and conquer". Anyway, from what I can see in the "T" file you provided, there are two major threats:
Bruno |
Dear Bruno,
Thanks for your quick answer! Quote:
Quote:
Well, now I could finally make it work I still have a problem. The problem is that the simulation starts running but after some time steps it crashes. Here you can see the last time steps for the fluid region (the one that make it crash): Code:
Time = 158
For more info, the case is about an air chamber that is heated by the solar radiation and the air inside the chamber flows because of the effect of the convection. If you need more info feel free to ask! ;) If I had more time I would have taken some screenshots so that you could see which cells lead to this crash. I will upload them as soon as I can! Regards, Alex |
Hi Alex,
:eek: temperatures below 0 Kelvin... It's very much possible that you're triggering an issue related to simulating heat transfer with a steady-state solver. This was addressed sometime ago in another thread... ah, here you go, start reading from here: http://www.cfd-online.com/Forums/ope...tml#post528307 post #60. And yes, the idea I was trying to give you was exactly about having the variable initializations at the top. And C++ is very similar to C, only just very much more organized... if coded correctly ;) And I knew that something wouldn't exactly as intended with changeDictionary :( I just couldn't remember what it was exactly. Either way, the thread I mentioned hopefully will get you in the right direction. Good luck! Best regards, Bruno |
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Hi Bruno,
Thanks for the link but it's not exactly the same problem since my case is a transient one, not steady-state. Now I've had some time I took some screenshots so that you can have an idea about my problem. Here you can see the geometry I used. http://www.cfd-online.com/Forums/att...1&d=1424098617 As you can see the air region is in the front, and the solid regions are just right behind it (the outline can be seen so that you can have an idea of my geometry). Attached you can find the temperature distribution for the last time step before it crashed. Also the U distribution is attached. As it is shown, the problem comes from the cells near the inlet patch, an extremely high velocity going out of the domain leads to an unphysical temperature distribution in the neighbouring cells, at least this is what it seems to my unexperinced eyes in the field of compressible flow in an opened domain... I have tried with different discretizations, with a coarser mesh but it allways crashes, sometimes sooner, sometimes later, but it crashes all the time... I don't know if it is a problem of the mesh or a bad definition of the BC's (specification can be seen some posts above!). I need a little help to find the correct way to make it run. Many thanks in advance. Regards, Alex |
Quote:
moving on ... have you checked that the regions are really conformal? (assuming this not AMI) and you havent gained an extra region? I remember this causing similar issues. |
Hello,
Finally I managed to "solve" it. The problem was, I guessed, the Courant number. The fact is that I was solving the case using a fixed time step of, if I'm not wrong, 1s. It was not causing any trouble during the first time steps but after a few time steps the Courant number started raising until the end of the simulation leading this to totally unphysical values. When I found it out I started the run with a deltaT of 0.2s during the first second to get it started and afterwards I switched the parameter adjustTimeStep to yes and maxCo to 0.9 in order to get better values for my simulation. Obviously, I got an improved temperature distribution but they are not totally correct yet. Here you can see the result I got, temperature minimums are not as unphysical as they were, but they are not physical at all yet. Thanks for your help and time. Regard, Alex |
Hi foamers,
Is there any kind soul to help me solve this problem? I am getting this error while running. I know the problem is coming from boundary condition but I do not know what should I do further. Please help. Code:
#0 Foam::error::printStack(Foam::Ostream&) at ??:? Thanks in advance.................. |
Quote:
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dear all,
i'm still facing a crach of the chtMultiRegionSimpleFoam after 5 time steps here the end of the log file: any suggestion will be very welcome, thank by advance .. Code:
Time = 4 |
Please revise your boundary conditions.
Also, please check user manual for max number of iterations setting, that you may set unintensionally. |
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hi Ahmed,
thank very much for helping. i post one of the many BC i have try... and a little drawing of the physical problem, gaz going through a pipe. i could not find where to increases the maximum number of iteration... the solution is may be to run a transient solver first? |
Hi Laurant,
I think you have a problem with your air velocity and pressure boundary conditions. Try converting inlet pressure and outlet velocity to zero gradient |
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the simulation is running only with laminar option, but the velocity of air goes up to 59 m/s ... for 1m./s at inlet
and if i turn kEpsilon option after 4 times step i got: Quote:
|
Greetings to all!
I had this thread on my to-do list because of laurent98's questions and I finally today managed to take a look into it. Unfortunately, since almost no information was provided about the case set-up, I'm not able to even try and guess what's wrong :( @laurent98: If you have not yet solved this problem in your case, then please follow the instructions given on this thread: http://www.cfd-online.com/Forums/ope...-get-help.html Best regards, Bruno |
Bruno,
I know this is an old thread but I am facing the exact problem. I'm trying to solve a heat exchanger problem using chtMultiRegionSimpleFoam and the temperature goes to -90 and then it crashes. I opened a new thread a while ago and didnt get any response over there (http://www.cfd-online.com/Forums/ope...implefoam.html) Going through different threads I found out maybe if I run my model as transient for a few time steps and then use that data as my IC it would work. Which it didnt and I am getting the following error: Code:
/*---------------------------------------------------------------------------*\ (http://www.cfd-online.com/Forums/ope...implefoam.html) Thanks Ali |
have you changing the values of the
nNonOrthogonalCorrectors or the relaxationFactors in system/fluid_region/fvSolution? a resource that helped me step up and solve such issues was this http://www.dicat.unige.it/guerrero/o...sandtricks.pdf Cheers, derek Code:
SIMPLE |
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Hi Bruno,
thank you very much for your interest, i didn't solve my problem with openfoam yet but i made a simplest computation by hand with classical thermic formulations. please find attach a general presentation of the problem. i'am sorry to not be on my computer now, i have not access right now to my OF's files best regards Laurent |
Derek,
Thanks for the response. I actually did play with the relaxation factors a lot! My last test was that I fixed the temp. every where to see if the solution still explodes which it did! So, now I'm looking different ways to see if I can find some answers for my problem. |
Hi Laurent!
As per the little information you provided related to your error some posts above, it seems that you are probably using an excessively high time step. Some time ago I faced a very similar problem to yours and setting adjustTimeStep to yes in controlDict helped me a lot! Besides that, check that your inlet and outlet BC's are the proper ones. Hope it helps you a little with your struggle! Best regards, Alex |
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