[MiriDR]

Hello,
while running my simulation i get the following Warning:

--> FOAM Warning :
From function Foam::scalar Foam::janafThermo<EquationOfState>::limit(Foam::sc alar) const [with EquationOfState = Foam:erfectGas<Foam::specie>; Foam::scalar = double]
in file /home/pawan/OpenFOAM/OpenFOAM-v1812/src/thermophysicalModels/specie/lnInclude/janafThermoI.H at line 117
attempt to use janafThermo<EquationOfState> out of temperature range 200 -> 5000; T = -388.868
--> FOAM Warning :
From function Foam::scalar Foam::janafThermo<EquationOfState>::limit(Foam::sc alar) const [with EquationOfState = Foam:erfectGas<Foam::specie>; Foam::scalar = double]
in file /home/pawan/OpenFOAM/OpenFOAM-v1812/src/thermophysicalModels/specie/lnInclude/janafThermoI.H at line 117
attempt to use janafThermo<EquationOfState> out of temperature range 200 -> 5000; T = -111.631
min/max(T) = 200, 1742.55

any idea on the reason why i get that?
Thanks.

[Yann]

Hello Miriana,

The warning you get means the temperature somewhere in your domain is out of the valid temperature range of the Janaf tables.
As you can see in the warning, the Janaf table is valid for temperature ranging from 200 to 5000K.

You seem to get negative temperature which is quite unphysical.

It's hard to help you more without knowing what you're trying to simulate, but most of the time this is due to inappropriate boundary conditions leading to divergence.


On a side note, please do not post the same question on several topics. I advise you to read the Guide: How to ask a question on the forums.

Yann

[MiriDR]

Hello Yann,
thank you for your answer and advice.

i know there could be some problems on the BC, but I can't figure it out where exactly. I'm simulating a gas dispersion, I set:

- velocity Field value,
- velocity inlet value,
- Temperature Field value,
- Temperature Inlet value.

the simulation does not give me warning during the first Time steps, but after a certain time it comes out with the janaf warning.

[Yann]

What solver are you using?


Could you post the detail of the BC you are using? (inlet and outlet)

What BC do you use for pressure?

[MiriDR]

I'm using SmallPoolFire3D.
The BC i set are:

Velocity - U
internalField uniform -5; (because i'm calculating on the opposite orientation of x-axes)
sides type pressureInletOutletVelocity;
value uniform (0 0 0);

walls type noSlip;

inlet type fixedValue;
value uniform (-0.05 0 0);

outlet type pressureInletOutletVelocity;
value uniform (0 0 0);

Temperature - T
internalField uniform 298.15;

sides
{
type inletOutlet;
inletValue $internalField;
value $internalField;

}
walls
{
type zeroGradient;
}


inlet
{
type fixedValue;
value uniform 313.15;
}
outlet
{
type inletOutlet;
inletValue $internalField;
value $internalField;

}
Pressure - p
internalField uniform 101325;

sides
{
type calculated;
value $internalField;
}

inlet
{
type calculated;
value $internalField;
}
outlet
{
type calculated;
value $internalField;
}
}

in the folder Constant i changed the g value to

dimensions [0 1 -2 0 0 0 0];
value (0 9.8 0);

Because after translating the geometry from fluent, it is upside down, so the dispersion is directed in the opposite side of the y-axes. meaning that g is positive according to the y-axes orientation.

[Yann]

Just to be clear, smallPoolFire3D is a tutorial and it uses the fireFoam solver.

What have you modified on the smallPoolFire3D tutorial?
As I understand, you changed the geometry and you use one coming from fluent, am I right? How does your domain look like?

about your pressure BC, fireFoam use the p_rgh pressure, defined as:



This is why all the BC in your p file are set to "calculated". You have to define your BC in the p_rgh file.

Could you post more information about your domain and set up? Or maybe upload a light version of your case if possible, so people can give a look at it and maybe help your to solve your problem?

You can have a look at this topic to see what kind of information can be useful for other users to help you. In addition, please use the CODE tags when you post your BC or other OpenFOAM files snippets in order to improve the readability of your posts.


I am not very familiar with gas dispersion but is there a specific reason for choosing fireFoam over other solvers?


Yann

[MiriDR]

Yes, i use smallPoolFire3D tutorial and fireFoam solver!!!
here's the geometry:
https://www.dropbox.com/s/5px442yfvm...ageom.PNG?dl=0

The inlet is the top of the highest tank, the outlet is the top of the domain.

I modified:

Velocity;
Temperature;
g
and of course the mesh.

I haven't changed the pressure, cause i need atmospheric pressure inside my domain.

I'm using fireFoam because I need further calculation on fire spreading.

Thank you.

[Yann]

Ok thank you I understand your choice now.

About your velocity BC on the inlet, you say you set:

type            fixedValue;
value           uniform (-0.05 0 0);

But if your inlet is the top of the highest tank, shouldn't you have a positive value on the y axis?

value           uniform (0 0.05 0);

Since you changed your geometry and coordinate system, you also may have to adjust the constant/hRef to the value of the highest point in your domain.

[MiriDR]

I put the value

type            fixedValue;
value           uniform (-0.05 0 0);

because i have the gas dispersion in the opposite direction of the x-axes.
Do you mean it cannot work if I choose the path to be on the x-axes, while the outlet is on top of the domain, parallel to the x-axes?

constant/href it refers to the top of the domain? i didn't know that!


thanks a lot.

[Yann]

If your inlet patch is horizontal (normal to y) and your BC imposes the velocity component Uy to be 0 on the patch it means there will be not flux through this patch.

I'm not very familiar with the prghTotalHydrostaticPressure BC but this is what I guess from the description of the BC and from tutorials using this BC. (oppositeBurningPanels for instance)
Maybe some other users who are more familiar with it can confirm that.

[prakash19971]

Hello MiriDR,
I am facing the same problem from quiet a while could you please provide some information on how did you manage to solve it if you have of course.
Thank you in advance