[kar]

Hello,

When I try to set BC type fixedGradient:

boundaryField
{
walls
{
type fixedGradient;
value uniform 0;
}
...
}

in 0/T file for temperature, after executing my solver I get this:
--> FOAM FATAL IO ERROR : keyword gradient is undefined in dictionary "/home/cpp/OpenFOAM/cpp-1.4.1/run/caurule/PUT/0/T::walls"

How should I define it or what else could be wrong?

K.

[mike_jaworski]

Karlis,
The problem is indicated in the error message: keyword gradient is undefined.
The fixedGradient boundary condition should look like this:

boundaryField
{
walls
{
type fixedGradient;
gradient uniform 0;
}
...
}

i.e. there's a "keyword" of "value" used with fixedValue and a "keyword" of "gradient" used with fixedGradient BCs respectively.

Good luck,
Mike J.

[kar]

Funny, right?

Where I could find that in code? find gives me a lot about "fixedGradient".

[mike_jaworski]

Karlis,
In order to answer your question, I'd have to have a lot more knowledge of OpenFOAM than I currently do. I'm still a newbie as well. I believe that it'll be in the neighborhood of this file:

http://foam.sourceforge.net/doc/Doxy...hField_8H.html

Regards,
Mike J.

[olwi]

Hi Karlis,

The information you needed is actually in the User's Guide. See Table 6.3 of Section 6.2.3.

In this particular case, the answer was in the written documentation, but that is admittedly not always the case with an open-source project like OpenFOAM. Still, I think OpenFOAM is one of the very few CFD codes that can crasch and give you a useful error message! In this case that the keyword "gradient" was missing...

I use Fluent more often than OF, and I assure you that the error messages I get there are completely useless. Most of the time the process just dies on me...

Good foaming!

/Ola

[JuanRodriguez]

Hi, Karlis.
Why would you use a fixedGradient of value 0 when there is the zeroGradient b.c.?
Perhaps that old version of OF didn't contain zeroGradient.
If the reason is more complex please let me know.
Thank you.