[charlliemarshalll]

Version:
OpenFOAM 7 v1912

Background:
I was trying to replicate the OpenFOAM validation case in this paper:

"Conjugate heat transfer of backward-facing step flow: A benchmark problem revisited" by Matjazˇ Ramšak

Problem:
Although I have double-checked everything, I cannot get the case converge. I have checked all the tutorial cases to borrow the configurations, but none worked.

Info:
The case is uploaded. Just run the Allrun file.

The error log produced by chtMultiRegionFoam is as follows:

====
Solving for fluid region water
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCGStab: Solving for h, Initial residual = 1, Final residual = 1.2406221e-11, No Iterations 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::hConstThermo<Foam::rhoConst<Foam::specie> >; Type = Foam::sensibleEnthalpy; Foam::scalar = double; Foam::species::thermo<Thermo, Type> = Foam::species::thermo<Foam::hConstThermo<Foam::rho Const<Foam::specie> >, Foam::sensibleEnthalpy>]
in file /home/ubuntu/OpenFOAM/OpenFOAM-7/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 70
Energy -> temperature conversion failed to converge:
iter Test e/h Cv/p Tnew
0 0 0 4181 -1.4382206e-22
1 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
2 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
3 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
4 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
5 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
6 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
7 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
8 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
9 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
10 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
11 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
12 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
13 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
14 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22
15 -1.4382206e-22 -6.0132005e-19 4181 -1.4382206e-22

....

--> FOAM FATAL ERROR:
Maximum number of iterations exceeded: 100

...

in file /home/ubuntu/OpenFOAM/OpenFOAM-7/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 106.

[crubio.abujas]

Hi charlliemarshalll,

It seems that you are applying unrealistic temperatures to the problem, varying the T field between 0 and 1. I guess that the paper have adimensional number and you're trying to supply the same conditions directly. All the thermal properties are apparently introduced as S.I variables: solid_cp 450 J/kg? solid_rho=8000 kg/m3? It seems that they are rather S.I values or too extreme adimensional ones.

I've tried using more reasonable T values [300K for the water an 600K for the wall] and not found any problem. You can put numbers into the paper formulas and solve for an specific case or try to convert the thermo properties into adminesional ones.

Hope it helps!

[ashansellum]

I might be late, but I think the error might be because of the initial temperature field. You could try with a non-zero internalField for temperature for both the heater & water. Try to keep the internalField value between 0 & 1 for faster convergence.