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January 14, 2014, 16:28 |
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#41 |
New Member
Bernhard
Join Date: May 2012
Location: Freiburg/Germany
Posts: 7
Rep Power: 14 |
Unfortunately I do not get beyond 0.07 seconds before the pressure blows up. If have attached the new version with the modified Allrun script. Switching off the turbulence does not make any difference...
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January 15, 2014, 12:32 |
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#42 |
New Member
Bernhard
Join Date: May 2012
Location: Freiburg/Germany
Posts: 7
Rep Power: 14 |
I am able to run that case if I change the BCs for p_rgh for bottom and wall to buoyantPressure and the one for top to fixedValue. Additionally I use funkySetField to initialize p. I have to use a lot of outerCorrectors (~30) at the beginning and underrelaxation, especially for p_rgh.
The velocity profile at the wall, due to the heat loss, is not as distinctive as before with buoyantBoussinesqPimpleFoam (see post #36). While the velocity profile is well developed in the lower region (after 360 sec), there are some disturbances in upper region probably caused by the BC for the top face. UY.jpg T1.jpgThot.jpg Tcold.jpg At least the temperature distribution is stable and quite uniform in radial direction (except at the outer wall with the heat flux) which was previously not the case. Does anyone have an idea which BCs might be as well appropiate for a closed tank? Even though the case is running with the current BCs, it is probably a wrong setup since there is still some velocity (see Fig. 2, UY) at the top face where it should actually be zero... |
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January 15, 2014, 17:07 |
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#43 |
Super Moderator
Tobias Holzmann
Join Date: Oct 2010
Location: Bad Wörishofen
Posts: 2,711
Blog Entries: 6
Rep Power: 52 |
Hi Bernhard,
I tryed several options. - changing 0/ files - changing initialization - changing thermodynamicProperties (with air its working) - test case with cht - test case with buoyant - test case with boussinesq - testings with diverent meshes - testings with several fvSolution options - changing pEqn.H in buoyantPressure - checking with laminar and turbulent flow characteristics Summary: - most simulations have a continuity problem (U_x,y,z) blow up and p_rgh too - re-coarse the mesh did not solve the problem - thermodynamics changing to perfectGas with air is working - changing p_rgh (top) to fixedValue is working but the results are bad. At the moment I am out of ideas - sorry. |
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January 16, 2014, 05:13 |
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#44 |
New Member
Bernhard
Join Date: May 2012
Location: Freiburg/Germany
Posts: 7
Rep Power: 14 |
Thanks for all your efforts, I also think that the thermophysical model is the problem. If I set the second coefficient for rho to zero the case is working...
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March 3, 2014, 16:00 |
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#46 | |
Senior Member
Nicolas Edh
Join Date: Mar 2010
Location: Uppsala, Sweden
Posts: 123
Rep Power: 18 |
Quote:
I might have an explanation of why the solution diverges when the density is non-constant and dpdt is on. I am hoping for your comments. By using icoPolynomial we are setting the fluid as incompressible, i.e. . So we have, by definition: Which is what icoPolynomial returns when the function psi is called. For an ideal gas is returned. The compressibility can be expanded to or So if we have non constant density, and hence must diverge? Perhaps we would need and compressiblePolynomial class where the compressibility can be set even though it's really small for water? Any thoughts? Cheers Nicolas |
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October 31, 2014, 09:33 |
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#47 |
New Member
Ezequiel Fogliatto
Join Date: Aug 2012
Posts: 1
Rep Power: 0 |
Hi Bernhard,
I'm facing a similar problem when I try to use icoPolynomial in a closed cavity. Could you solve your case? |
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December 4, 2014, 04:59 |
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#48 |
New Member
MK
Join Date: Oct 2014
Posts: 6
Rep Power: 12 |
Hi,
What kind of boundary conditions did you use? Could you be so nice and tell me which BC you used for the simulation with buoyantSimpleFoam, specially p and p_rgh. I am confused about these BC. I have changed the solver as recommended by Tom in the post. Have a nice weekend, MK. |
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December 26, 2014, 09:49 |
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#49 | |
Member
a
Join Date: Nov 2013
Posts: 34
Rep Power: 13 |
Quote:
I have continuity error with buoyantSimpleFoam how did you change the schemes? thanks |
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February 7, 2017, 10:48 |
BuoyantPimpleFoam crashes when using polynomial thermophysical properties
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#50 | |
New Member
Antoine
Join Date: Jan 2016
Posts: 6
Rep Power: 10 |
Hi everyone,
I am using OpenFOAM 4-1 and I would like to run the buoyantPimpleFoam tutorial "hotroom" with the polynomial properties. The problem is the same as many of you got earlier which is that the solver crashed after few iterations (here 1 ...) and which is the following: Quote:
*refining the mesh *changing the pressure initialization in the solver or using funkySetFields to initialize the pressure *modifying the relaxation factors in the fvSolution as well as increasing the number of inner and outer correctors *using dpdt off/no However, none of these solutions was solving my problem. Has someone already had this problem before and solved it? Or do you have other any trick I could try to make it work? Many thanks, Antoine |
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February 7, 2017, 11:01 |
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#51 |
Super Moderator
Tobias Holzmann
Join Date: Oct 2010
Location: Bad Wörishofen
Posts: 2,711
Blog Entries: 6
Rep Power: 52 |
Dear Antionio,
please start with dt = 1e-7. You first time step is too big and therefore the courant number explodes already: Courant Number mean: 9.24507 max: 26.4701. That would be my first guess. Especially because you run in PISO mode Code:
PIMPLE: Operating solver in PISO mode
__________________
Keep foaming, Tobias Holzmann |
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February 7, 2017, 11:21 |
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#52 | |
New Member
Antoine
Join Date: Jan 2016
Posts: 6
Rep Power: 10 |
Thanks for your quick answer Tobi.
Yes I tried this as well and the solver crashes during the third time step. Here is the log file. Quote:
Antoine |
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February 7, 2017, 11:29 |
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#53 |
Super Moderator
Tobias Holzmann
Join Date: Oct 2010
Location: Bad Wörishofen
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Rep Power: 52 |
Your p_rgh solver has problems:
Code:
DICPCG: Solving for p_rgh, Initial residual = 0.95771, Final residual = 12.2972, No Iterations 1001
Good luck,
__________________
Keep foaming, Tobias Holzmann |
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February 9, 2017, 08:51 |
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#54 |
New Member
Antoine
Join Date: Jan 2016
Posts: 6
Rep Power: 10 |
Thanks for your advice Tobias. I will investigate.
Cheers, Antoine |
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July 17, 2017, 15:07 |
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#55 |
New Member
Antoine
Join Date: Jan 2016
Posts: 6
Rep Power: 10 |
Dear All,
In case some of you are interested, the problem was while using polynomial density or boussinesq approximation in the case of a closed volume with buoyantPimpleFoam. The bug was reported and corrected in the lastest version of OpenFOAM-dev. (https://bugs.openfoam.org/view.php?id=2617) Best regards, Antoine |
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June 16, 2018, 14:21 |
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#56 |
Senior Member
Artur
Join Date: May 2013
Location: Southampton, UK
Posts: 372
Rep Power: 20 |
Hi All,
I know this is a bit of an old thread but I'm struggling with the exact same issue as Tobi did, namely when I try to simulate a hot water jet entering a large body of water with polynomial equations for state my density solution exceeds the maximum no. iterations. I'd like to simulate something similar to this thesis: http://www.diva-portal.org/smash/get...421/FULLTEXT01 I gather it's the polynomials themselves that are causing the issue but I'm clueless as to how to fix this. Does anyone have any successful example cases for such a problem? Funnily enough, my case works fine with buoyantBoussinesqSimpleFoam. Thanks, Artur |
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June 16, 2018, 16:15 |
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#57 |
New Member
Antoine
Join Date: Jan 2016
Posts: 6
Rep Power: 10 |
Hi!
Which version are you using? I think the bug I mentioned in a previous post was corrected in OpenFOAM 4.x. Otherwise is the term dpdt set to off or no in your thermophysical file? Regards, Antoine Last edited by antoine_hub; June 17, 2018 at 06:28. |
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June 16, 2018, 16:56 |
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#58 |
Senior Member
Artur
Join Date: May 2013
Location: Southampton, UK
Posts: 372
Rep Power: 20 |
Hi,
Thanks for the prompt reply. I'm using 5.0 and at the moment not, I didn't have the unsteady term switched off. I'll try to see how to do it but if you could let me know that would also be great Artur EDIT: okay, just tried and it didn't change anything. I also tried to fix the density, viscosity, kappa and Cp by setting the constant term of the polynomials to the correct value and the rest to zero but to no avail. EDIT 2: I posted my case with the mesh here, if anyone who knows more about this category of solvers would like to have a look it'd be much appreciated! https://www.dropbox.com/s/b4hu90ajdn...le.tar.gz?dl=0 |
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June 22, 2018, 03:39 |
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#59 |
Senior Member
Artur
Join Date: May 2013
Location: Southampton, UK
Posts: 372
Rep Power: 20 |
Hi All,
After some intense figuring out and help from Antoine I managed to get the case working. The trick seems to be in using a temperature and velocity limiter for the first few iterations to allow the solver to cope with the admittedly complicated BC set up that my case has. You just need to put the attached fvOptions file in the constant directory and then comment the limiters out later on (or just make sure the limits have a sensible margin in the first place I guess). All the best, A fvOptions.txt |
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