[boffin5]

Hello again,


After receiving greatly appreciated help in setting up a radiator-in-a-duct case, I set about putting it to use in a real task. It ran successfully with one specified radiator temperature, but when I changed T to a different value, it failed; here is a snippet of the output message:

          [1] 68       1069.52        397373       1162.17        1068.2
          [1] 69        1068.2        394396       1162.06       1069.45
          [1] 70       1069.45        397209       1162.16       1068.27
          [1] 71       1068.27        394551       1162.06       1069.38
          [1] 72       1069.38        397064       1162.16       1068.33
          [1] 73       1068.33        394689       1162.07       1069.33
[1] 
[1] 
[1] --> FOAM FATAL ERROR: 
[1] Maximum number of iterations exceeded: 100
[1] 
[1]     From function Foam::scalar Foam::species::thermo<Thermo, Type>::T(Foam::scalar, Foam::scalar, Foam::scalar, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar) const, bool) const [with Thermo = Foam::hPolynomialThermo<Foam::icoPolynomial<Foam::specie> >; Type = Foam::sensibleEnthalpy; Foam::scalar = double; Foam::species::thermo<Thermo, Type> = Foam::species::thermo<Foam::hPolynomialThermo<Foam::icoPolynomial<Foam::specie> >, Foam::sensibleEnthalpy>]
[1]     in file /home/ubuntu/OpenFOAM/OpenFOAM-8/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 106.

So I figured that there was a problem with boundary conditions, so tweaked some of them. Now, it fails every time, and I can't get back to the version that ran okay. (Note to self - when it runs properly, save it!!) But even then, the BCs apparently had a problem.


To make it easy to see where I'm at currently, I collated my BCs and some schematics on the attached Excel file. Also attached is the run script for the case.



I need help with finally getting a handle on the proper set of boundary conditions. The tutorials give a little help, but don't really cover my case, and I have fought with this at length, and with little success.


Hoping for help, and/or pointing to the right set of resources.

[boffin5]

I am continuing to struggle with my chtMultiRegion radiator simulation case. My simple template case seems to work, but when I put in more complex geometry, it fails with the "maximum number of iterations exceeded:100" message.


Attached is an image that shows the geometry I'm working with. It's basically an airplane fuselage with a radiator in a ventral fairing. To assess the mesh, I took out the radiator and ran it as a simpleFoam case, and it worked. But with the radiator, it always fails. My boundary conditions are defined in my previous post.


Now, my theory is that in the overlapping region, the solid and fluid cell sizes should be similar. In the image, the relative cell sizes can be seen, with the two regions shown separately. They are close, but not identical. Again, the run failed. Is my mesh theory correct? If so, how close should the cell sizes be?


I am hammering away at this, but not getting anywhere. But I will not give up!! Nevertheless, am hoping for some advice to save me time and frustration.

[Kummi]

I didn't read your entire contents posted here. To be more precise, are you looking for Coupling boundary condition between the multiregions ? Have you refereed multiregion tutorials for appropriate boundary conditions and relevant forum pages ?
Thank you

[boffin5]

My case is a porous solid zone , immersed in a fluid zone, so it should be coupled? At any rate, based on your observation, I looked at the heatExchanger tutorial in v2012 (I typically use OF8), and noted that the alphat BC had the format that you referred to. So I used that tutorial as a template for my boundary conditions. Unfortunately, it failed again, with the same "maximum number of iterations" message. Here is part of the runlog:

Region: fluid Courant Number mean: 241.035 max: 74441.5
Region: solid Courant Number mean: 0.043849 max: 0.698227
Time = 2


Solving for fluid region fluid
DILUPBiCGStab:  Solving for Ux, Initial residual = 0.0375302, Final residual = 0.00117791, No Iterations 1
DILUPBiCGStab:  Solving for Uy, Initial residual = 0.0561504, Final residual = 0.00239053, No Iterations 1
DILUPBiCGStab:  Solving for Uz, Initial residual = 0.20625, Final residual = 0.00923548, No Iterations 1
DILUPBiCGStab:  Solving for h, Initial residual = 0.947747, Final residual = 0.093489, No Iterations 5

    From function Foam::scalar Foam::species::thermo<Thermo, Type>::T(Foam::scalar, Foam::scalar, Foam::scalar, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar, Foam::scalar) const, Foam::scalar (Foam::species::thermo<Thermo, Type>::*)(Foam::scalar) const, bool) const [with Thermo = Foam::hPolynomialThermo<Foam::icoPolynomial<Foam::specie> >; Type = Foam::sensibleEnthalpy; Foam::scalar = double; Foam::species::thermo<Thermo, Type> = Foam::species::thermo<Foam::hPolynomialThermo<Foam::icoPolynomial<Foam::specie> >, Foam::sensibleEnthalpy>]
    in file /home/ubuntu/OpenFOAM/OpenFOAM-8/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 70
    Energy -> temperature conversion failed to converge:
          [0] iter          Test           e/h          Cv/p          Tnew
          [0] 0        551.55       -161588       1049.09       1083.62
          [0] 1       1083.62        208023       1163.19       1245.74
          [0] 2       1245.74        740039       1146.09       946.085
          [0] 3       946.085        -44205       1142.75       1331.83
          [0] 4       1331.83        955187       1106.82       827.155
          [0] 5       827.155        -76472       1113.93       1251.85
          [0] 6       1251.85        757385       1144.13       936.514
          [0] 7       936.514      -50041.2       1140.67       1328.08
          [0] 8       1328.08        947052        1109.1       831.775

It always fails at time step 2, so there is something fundamental going on, but I am at a loss.


Attached is an excel file that shows all of the patch boundary conditions, as well as the initial conditions.


Truly hoping for help, so I can get past this logjam!

[Kummi]

Checking your error at line number 70 in thermoI.H

Energy -> temperature conversion failed to converge:

https://cpp.openfoam.org/v7/thermoI_...C%3C%20endl%3B
This solves temperature (T) variable using Newton-Raphson method. That's clear for now.
Here the links that might help you.
chtMultiRegionFoam "thermoI.H" Not Converging
Highly unstable buoyantPimpleFoam simulation
Have you came across the posts ? Thank you