[olivierdambron]

Hi guys I'm running buoyantSimpleFoam for a solar chimney. I am basing my case on the tutorial 'hotRadiationRoom' to which I add an inlet and an outlet.
I am getting the following error, any chance you guys know how I can move forward? I attach hereby my /0 folder with my BC.








// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time
Create mesh for time = 0
SIMPLE: convergence criteria
field p_rgh tolerance 0.01
field U tolerance 0.001
field h tolerance 0.001
field G tolerance 0.001
field "(k|epsilon|omega)" tolerance 0.001
Reading thermophysical properties
Selecting thermodynamics package
{
type heRhoThermo;
mixture pureMixture;
transport const;
thermo hConst;
equationOfState perfectGas;
specie specie;
energy sensibleEnthalpy;
}
Reading field U
Reading/calculating face flux field phi
Creating turbulence model
Selecting turbulence model type RAS
Selecting RAS turbulence model kEpsilon
RAS
{
RASModel kEpsilon;
turbulence on;
printCoeffs on;
Cmu 0.09;
C1 1.44;
C2 1.92;
C3 0;
sigmak 1;
sigmaEps 1.3;
}
Reading g
Reading hRef
Calculating field g.h
Reading field p_rgh
No MRF models present
Selecting radiationModel P1
Selecting absorptionEmissionModel constantAbsorptionEmission
Selecting scatterModel none
Selecting sootModel none
No finite volume options present
Starting time loop
Time = 1
.....
Time = 4
Duration of pickling 0.0978538990021 too long. Extending frequency from 1.0 to 4.8926949501
DILUPBiCGStab: Solving for Ux, Initial residual = 0.2111138, Final residual = 7.33545e-05, No Iterations 1
DILUPBiCGStab: Solving for Uy, Initial residual = 0.4600708, Final residual = 0.0002523532, No Iterations 1
DILUPBiCGStab: Solving for Uz, Initial residual = 0.352951, Final residual = 0.0001029493, No Iterations 1
DILUPBiCGStab: Solving for h, Initial residual = 0.0007439446, Final residual = 2.572517e-07, No Iterations 1
[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) const [with Thermo = Foam::hConstThermo<Foam:erfectGas<Foam::specie> >; Type = Foam::sensibleEnthalpy; Foam::scalar = double; Foam::species::thermo<Thermo, Type> = Foam::species::thermo<Foam::hConstThermo<Foam:er fectGas<Foam::specie> >, Foam::sensibleEnthalpy>]
[1] in file /home/ubuntu/OpenFOAM/OpenFOAM-5.x/src/thermophysicalModels/specie/lnInclude/thermoI.H at line 73.
[1]
FOAM parallel run aborting

[clapointe]

It looks like the velocity and pressure boundary conditions have not been changed from the tutorial case -- it was created to simulate heat transfer inside a closed room. If you want to allow flow in/out of the domain, you will need to change them.

Caelan

[olivierdambron]

HI Caelan,

Thanks for the reply. I would like just to input temperature and monitor velocity and pressure.

What kind of BC for U, p and prgh would you recommend?

For U:
outlet
{
type pressureInletOutletVelocity;
value uniform (0 0 0);
}
inlet
{
type pressureInletOutletVelocity;
value uniform (0 0 0);
}

For p:
outlet
{

type calculated;
value uniform 100000;

}

inlet
{

type calculated;
value uniform 100000;

For p_rgh:
outlet
{

type fixedValue;
value uniform 100000;


}

inlet
{
type fixedFluxPressure;
value uniform 100000;

[clapointe]

Those are starting to look more like what you'd want. They might work -- you might also try total pressure (for pressure) and inlet outlet (for velocity) and see if the results look physical.

Caelan

[olivierdambron]

I also have to change my fvschemes. I'm a bit in the dark, is this ok? without it the temperature dives big negative and crashes.


This is what I'm using at the moment

ddtSchemes
{
default steadyState;
}

gradSchemes
{
default cellLimited leastSquares 1;
}

divSchemes
{
default none;
div(phi,T) bounded Gauss linearUpwind default;
div(phi,U) bounded Gauss upwind;
div(phi,K) bounded Gauss upwind;
div(phi,h) bounded Gauss upwind;
div(phi,k) bounded Gauss upwind;
div(phi,epsilon) bounded Gauss upwind;
div(((rho*nuEff)*dev2(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
default Gauss linear limited corrected 0.333;
}

interpolationSchemes
{
default linear;
}

snGradSchemes
{
default limited corrected 0.333;
}




For comparison this is the one of the tutorial:

ddtSchemes
{
default steadyState;
}

gradSchemes
{
default Gauss linear;
}

divSchemes
{
default none;
div(phi,U) bounded Gauss upwind;
div(phi,K) bounded Gauss upwind;
div(phi,h) bounded Gauss upwind;
div(phi,k) bounded Gauss upwind;
div(phi,epsilon) bounded Gauss upwind;
div(((rho*nuEff)*dev2(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
default Gauss linear corrected;
}

interpolationSchemes
{
default linear;
}

snGradSchemes
{
default corrected;
}

[clapointe]

The schemes from the tutorial are a good place to start. They're mostly first order so you can change them to be less diffusive once you have the case running.

Caelan

[olivierdambron]

Caelan, many thanks for the help.

When I use the tutorial's scheme , my temperature dives to extremes and goes negative. I'm really unsure of how to make it less diffusive, any chance you could let me know? or point me to some relevant reading?

sorry for being a bit assisted here.

[clapointe]

It's most likely an issue with your case setup if the temperature immediately goes negative -- try changing your boundary conditions. This is a good place to start reading about setting up fvSchemes : https://www.openfoam.com/documentati.../fvSchemes.php.

Caelan

[olivierdambron]

Thanks Mate.

Olivier

[olivierdambron]

OK I've read the page and if I understand correctly, I made it less diffusive by changing :

laplacianSchemes
{default Gauss linear corrected;}

to

laplacianSchemes
{default Gauss linear limited 0.5;}

Its running well now.

thanks for pushiing me to find the answer!

[olivierdambron]

Dear Caelan,

although I have reduced the laplacian schemes to make it less diffusive, the simulation runs and diverges at time 90 for the same reason 'nb of iteration exceeded'.

Should I reduce even more?

laplacianSchemes
{default Gauss linear limited 0.5;}

[clapointe]

There are many potential ways to make the simulation less diffusive. However, it is hard to tell why your case is failing without seeing the whole thing -- can you include it?

[olivierdambron]

Here attached is the last version that runs until time 90.
after surfacefeatureextract,blockmesh,snappy,buoyantSimp leFoam.

If you could take a look it would really be of great help.

Olivier

[clapointe]

How are you running your case? There are only walls created by your blockMeshDict at the moment -- without further modification you will not have an inlet or outlet.

Caelan

[olivierdambron]

My case is a bit crafty using Butterfly on Grasshopper for Rhino. I write the case and then modify all using notepad.

Those walls you are seeing are the boundary volume, the following should make it run:

surfacefeatureextract,blockmesh,snappyhexmesh,buoy antSimpleFoam.

you may need to copy constant folders into the times. If you wish I could send you the meshed case more or less 170 mb. I could send you a wetransfer if needed.

[clapointe]

The case ran for me at significantly lower resolution, but I do not know enough about your problem to interpret the results. I expect you still have a problem with the case setup -- try looking at boundary conditions used for the buoyantSimpleFoam tutorials.

Caelan

[olivierdambron]

thanks for looking into it.

What Im trying to analyze is the volumetric flowrate induced by the buoyancy in the solar chimney. So Im inputing only temperatures which are taken form an thermodynamic model. pressures and velocity are what im looking for.

The BC used for buoyantSimpleFoam in the tutorial do not show for inlets and outlets.

[clapointe]

I should have been clearer -- other buoyantSimpleFoam tutorials have inflow/outflow. Like this one : https://github.com/OpenFOAM/OpenFOAM...itBoardCooling

[olivierdambron]

Dear Clapointe,

I've tried over and over again and I have to admit that Im a bit lost. Would you be keen on helping me set this case so I can refer to it for further iterations and learn from a steady base?

Kind regards,
Olivier

[clapointe]

I do not have time to work too much on your case, but I'd recommend that you keep working on the case setup -- boundary conditions leading to unphysical behavior are often the cause for crashes.

Caelan