[sabago]

Hello OpenFOAMers

I have a variable,x that is mapped in my code so it's a volScalarField and I would like to fix it in the transportProperties dictionary as a dimensionedScalar.

Originally, x was set in the 0 folder but I want to fix it in transportProperties so that it doesn't go to zero as it currently does.

I've seen a few posts about converting a dimensioned scalar to volScalarField but I wasn't successful with those methods.

Any ideas?

Best,
Sandra

[alexeym]

Hi,

Here is an example from laminar turbulence model:

        ...
        new volScalarField
        (
            IOobject
            (
                "nut",
                runTime_.timeName(),
                mesh_,
                IOobject::NO_READ,
                IOobject::NO_WRITE
            ),
            mesh_,
            dimensionedScalar("nut", nu()().dimensions(), 0.0)
        )
        ...

Did you try this constructor (you need to correct the name of the field, dimensions, and instead of dimensionedScalar(...) you should put the constant you have read from transportProperties dictionary)? What error did you get?

[sabago]

Originally Posted by alexeym

Hi,

Here is an example from laminar turbulence model:

        ...
        new volScalarField
        (
            IOobject
            (
                "nut",
                runTime_.timeName(),
                mesh_,
                IOobject::NO_READ,
                IOobject::NO_WRITE
            ),
            mesh_,
            dimensionedScalar("nut", nu()().dimensions(), 0.0)
        )
        ...

Did you try this constructor (you need to correct the name of the field, dimensions, and instead of dimensionedScalar(...) you should put the constant you have read from transportProperties dictionary)? What error did you get?

Hi Alexey!

Thank you for that contructor. Here's what I did

volScalarField jbvagCell
(
IOobject
(
"jbvag",
runTime.timeName(),
mesh,
IOobject::MUST_READ,
IOobject::AUTO_WRITE
),
mesh,
dimensionedScalar("jbvag", dimensionSet(0,-3,0,0,0,1,0), 2e6)
);
where 2e6 is the value that I want to fix.

wmake for the solver works fine. However, in the .H file where I use jbvag, I have
Info<<jbvag<<endl; to show me the values as the simulation proceeds and for some reason jbvag is zero.

Any thoughts please?


Best,
Sandra

[alexeym]

Hi,

Your volScalarField is called jbvagCell, in your output statement variable is jbvag. Also if you would like to create volScalarField from dimensionedScalar (so there is no need to create file in 0 folder), you should not use read-constructor (i.e. with IOobject::MUST_READ flag, as you can see in the example the flag has value IOobject::NO_READ).

[sabago]

Hello!

I don't have files in the 0 folder for this variable.
Here's what I have now

volScalarField jbvagCell
(
IOobject
(
"jbvagCell",
runTime.timeName(),
mesh,
IOobject::NO_READ,
IOobject::NO_WRITE
),
mesh,
dimensionedScalar("jbvagCell", dimensionSet(0,-3,0,0,0,1,0), 2e6)

jbvagCell still goes to zero when I check.

Sandra

[alexeym]

Hi,

Post your code or at least relevant parts. I can continue guessing what is wrong but I do not want to.

[sabago]

Hi Alexey!

Here's the equation that I'm trying to solve

jbvagCell = iagCell*((Foam::exp(alphaaa*F*EttaaCell/(Rg*T)))-(Foam::exp(-alphaca*F*EttaaCell/(Rg*T))));

where jbvagCell is the fixed value in the createFields.H; iagCell is calculated elsewhere just fine. alphaaa, F, Rg, T and alphaca are constants in the transportProperties.

And EttaaCell is what I'm solving for.

Please note that this equation cannot be rearranged such that EttaaCell is the subject of the equation.

Note: when I rewrite the equation as f(EttaaCell) = 0; jbvagCell is fixed but EttaaCell remains zero!

Many thanks in advance.

Sandra

[alexeym]

Hi,

Unfortunately during the whole thread you are trying to show how you create volume field. Yet the most interesting parts are elsewhere and it is not possible to deduce:

- What do you do with the field after creation?
- What do you mean by "...still goes to zero when I check."?
- How do you check the values of the field?
- When do you check these values?
- Are you sure you do not modify the field?

You have shown this piece of code:

jbvagCell = iagCell*((Foam::exp(alphaaa*F*EttaaCell/(Rg*T)))-(Foam::exp(-alphaca*F*EttaaCell/(Rg*T))));

From this I just can guess, that somewhere in your code, you update jbvagCell. If iagCell if 0, jbvagCell is 0. I do not know values of alphaaa, F, Rg, T, alphaca, so I can suppose, that alphaaa*F*EttaaCell/(Rg*T) == -infinity and -alphaca*F*EttaaCell/(Rg*T) == -infinity, so your exponents are 0 and again jbvagCell is 0.

[sabago]

-What do you do with the field after creation?
I set the field in createFields.H then use it in the above equation in a file.H and that's all I do with it.
- What do you mean by "...still goes to zero when I check."?
- How do you check the values of the field?
- When do you check these values?
In file.H, under the above eqn I have...

Info<<jbvagCell>>endl;
Info<<EttaaCell>>endl;
Info<<iagCell>>endl;

and that's how I track the values.

- Are you sure you do not modify the field?
I'm quite sure...the variable jbvagCell only appears twice; in the createFields.H and file.H

Sandra