[alimea]

Hi every body

I want to calculate average temperature in a laplacianFoam code (I know we have simpler ways to calculate it, I just want to learn programing).
1- I created a file "Average.H" in the solver folder and called it in solver.C by #include Average.H
2- in Average.H file I want to write a code similar to (this is what I want, but I don't know how it should be written in solver code in openFoam):
for n=1:1:N //for all the time steps

for i=1:1:I //for all the cells of domain

sum=sum+T(n,i); // after solving equation and finding T(n,i), calculate sum

end
Tave(n)=sum(n)/N; // At the end of every time step calculation, give me Tave (I want to plot it along the run process)

end

I know that I should use "forAll", but I don't know it's arguments and how it works! How I can calculate sum? Tave?

Thanks a lot

[paradox]

Dear alimea,

At the first you need to declare and initialize "Tave" in your createFields.H,

    dimensionedScalar T0("zero",dimensionSet(0, 0, 0, 1, 0, 0, 0),0);
    volScalarField Tave
    (
        IOobject
        (
            "Tave",
            runTime.timeName(),
            mesh,
            IOobject::NO_READ,
            IOobject::AUTO_WRITE
        ),
        mesh,
        T0
    );

Then in your file "Average.H" you can loop over all cells by forAll:

scalar totalTime = mesh.time().value();
scalar dt = mesh.time().deltaTValue();
forAll(Tave, i)
{
	Tave[i] = (totalTime * Tave[i] + dt * T[i] ) / (totalTime + dt);
}

I hope this work for you.
This is a simple code and suitable for start averaging at zero time starting, But you cat improve it by adding startTimeAveraging and a few conditions to work fine.

[alimea]

Originally Posted by paradox

Dear alimea,

At the first you need to declare and initialize "Tave" in your createFields.H,

    dimensionedScalar T0("zero",dimensionSet(0, 0, 0, 1, 0, 0, 0),0);
    volScalarField Tave
    (
        IOobject
        (
            "Tave",
            runTime.timeName(),
            mesh,
            IOobject::NO_READ,
            IOobject::AUTO_WRITE
        ),
        mesh,
        T0
    );

Then in your file "Average.H" you can loop over all cells by forAll:

scalar totalTime = mesh.time().value();
scalar dt = mesh.time().deltaTValue();
forAll(Tave, i)
{
	Tave[i] = (totalTime * Tave[i] + dt * T[i] ) / (totalTime + dt);
}

I hope this work for you.
This is a simple code and suitable for start averaging at zero time starting, But you cat improve it by adding startTimeAveraging and a few conditions to work fine.

Dear Mehdi
I'm really thankfull for this helpful information.

I have some other questions about your code. I hope not to make you tired:
1- what is the "zero" at
dimensionedScalar T0("zero",dimensionSet(0, 0, 0, 1, 0, 0, 0),0);

2- can I define Tave (as a volScalarField) in Average.H? or this is a rule that we have to define it in createFields.h?

3- why do we write "T0" at
),
mesh,
T0
);

4- when we define an IOobject in form of "NO_READ", it means it isn't read from initial and boundary condition?

5- I have a general problem with these type of notation in openFoam:
mesh.time().value()
mesh.time().deltaTValue()
what are these? what's the meaning of them? what do "mesh", deltaTValue() and ".value()" do?
when do we use ".value()", ".deltaTValue()"?
could you please tell me the general meaning of them to learn this notation for ever?

6- I saw in some codes "counter" insted of "i". is it arbitrary?

7- I didn't get tour sentence "This is a simple code and suitable for start averaging at zero time starting".

Again I really appreciate your help

[paradox]

1- what is the "zero" at
dimensionedScalar T0("zero",dimensionSet(0, 0, 0, 1, 0, 0, 0),0);

I think it's just the name of you variable and it's arbitrary.

2- can I define Tave (as a volScalarField) in Average.H? or this is a rule that we have to define it in createFields.h?

Tave should be create before and out of the loop. Average.H is in the loop.

3- why do we write "T0" at
),
mesh,
T0
);

T0 is the initialize value for Tave and is equal to 0.
you could also initialize Tave without declaring T0, like below:

),
mesh,
dimensionedScalar("Tave",dimensionSet(0, 0, 0, 1, 0, 0, 0),0)
);

4- when we define an IOobject in form of "NO_READ", it means it isn't read from initial and boundary condition?

Yes, that's right.

5- I have a general problem with these type of notation in openFoam:
mesh.time().value()
mesh.time().deltaTValue()
what are these? what's the meaning of them? what do "mesh", deltaTValue() and ".value()" do?
when do we use ".value()", ".deltaTValue()"?
could you please tell me the general meaning of them to learn this notation for ever?

mesh.time().value() return the time of your simulation.
mesh.time().deltaTValue() return return the time step of simulation.
You need to know more about object oriented programming.

6- I saw in some codes "counter" insted of "i". is it arbitrary?

Yes, it is arbitrary.

7- I didn't get tour sentence "This is a simple code and suitable for start averaging at zero time starting".

I said this algorithm work fine if you start simulation at zero, and is not suitable for averaging when you stop the run and start again from your last time.

I hope I didn't mistake in responding.

[alimea]

Originally Posted by paradox

I think it's just the name of you variable and it's arbitrary.


Tave should be create before and out of the loop. Average.H is in the loop.


T0 is the initialize value for Tave and is equal to 0.
you could also initialize Tave without declaring T0, like below:

),
mesh,
dimensionedScalar("Tave",dimensionSet(0, 0, 0, 1, 0, 0, 0),0)
);

Yes, that's right.


mesh.time().value() return the time of your simulation.
mesh.time().deltaTValue() return return the time step of simulation.
You need to know more about object oriented programming.

6- I saw in some codes "counter" insted of "i". is it arbitrary?

Yes, it is arbitrary.


I said this algorithm work fine if you start simulation at zero, and is not suitable for averaging when you stop the run and start again from your last time.

I hope I didn't mistake in responding.

Thanks for your complete answers.
How or where can I know about object oriented programming (I just want to know about that type of notation)?

If I want to write:
a=a+T[i]
(that a is a scalar variable) openFoam gives me the error that you can't sum a scalar variable with a tensor! How can I sum a scalar and a component of a volScalarFild (like temperature)?

Regards

[paradox]

If you want to be a programmer in openFOAM, I think you need to know more about programming in C++ and OOP. Internet is full of lecture about them and chalmers course, specially is good for starting.

If I want to write:
a=a+T[i]
(that a is a scalar variable) openFoam gives me the error that you can't sum a scalar variable with a tensor! How can I sum a scalar and a component of a volScalarFild (like temperature)?

This thread will be helpful for you.
How to get a single value from a volScalarField including the dimension

regards,
Mehdi

[alimea]

Originally Posted by paradox

If you want to be a programmer in openFOAM, I think you need to know more about programming in C++ and OOP. Internet is full of lecture about them and chalmers course, specially is good for starting.


This thread will be helpful for you.
How to get a single value from a volScalarField including the dimension

regards,
Mehdi

Thanks dear Mehdi
I had a mistake in my last post! I want to access to one of the members of a volScalarField like temperature and do some algebraic operation:

dimensionedScalar A("zero",dimensionSet(0, 0, 0, 1, 0, 0, 0),0);
dimensionedScalar B("zero",dimensionSet(0, 0, 0, 1, 0, 0, 0),5);
dimensionedScalar C("zero",dimensionSet(0, 0, 0, 1, 0, 0, 0),0);

forAll(A,i)
{
A=2*T(i)+B; // T(i) is one one of the members of temperature Field
}
C=A*6;

is it correct that I defined A as a scalar?
The compiler gave me the error:

error: ‘Foam::dimensionedScalar’ has no member named ‘size’
for (Foam::label i=0; i<(list).size(); i++)
^
Average.H:45:2: note: in expansion of macro ‘forAll’
forAll(aa, i)
^

Regards

[floquation]

Originally Posted by alimea

forAll(A,i)
{
A=2*T(i)+B; // T(i) is one one of the members of temperature Field
}
C=A*6;

is it correct that I defined A as a scalar?

First of, always use [CODE]-tags to show code.

Now for your question: if you wish to iterate over the content of a scalar, then your code does exactly what you want: "forAll(A,i) = for every element of (scalar) A". However, since every scalar comprises only one number, the loop doesn't actually loop. In fact, it gives you your error.
What you, presumably, wish to do is iterate over the elements of T?

forAll(T,i)

But then I do not understand what the loop does, as A is then simply overwritten in every iteration.

[alimea]

Originally Posted by floquation

First of, always use [CODE]-tags to show code.

Now for your question: if you wish to iterate over the content of a scalar, then your code does exactly what you want: "forAll(A,i) = for every element of (scalar) A". However, since every scalar comprises only one number, the loop doesn't actually loop. In fact, it gives you your error.
What you, presumably, wish to do is iterate over the elements of T?

forAll(T,i)

But then I do not understand what the loop does, as A is then simply overwritten in every iteration.

Ohhh! thank you. it was wrong! I had to write: forAll(T,i)

This was for testing code tag :o

[sippanspojk]

I want to do something similar as what Alimea did but I would like to loop over the pressure values of each face of a patch instead of the temperature. I am also quite new to C++ and to programming in OpenFOAM so please bare with me if my questions are trivial.

I have defined myFunctionObj.C and myFunctionObj.H as I understand from

At the first you need to declare and initialize "Tave" in your createFields.H,

    dimensionedScalar T0("zero",dimensionSet(0, 0, 0, 1, 0, 0, 0),0);
    volScalarField Tave
    (
        IOobject
        (
            "Tave",
            runTime.timeName(),
            mesh,
            IOobject::NO_READ,
            IOobject::AUTO_WRITE
        ),
        mesh,
        T0
    );

I should define my volScalarField (adapted to my variables and correct units) in my myFunctionObj.H file, correct?

I do have some questions about this though and correct me if I'm wrong:
- Firstly, am I defining a scalarField named "Tave" with units K that I can reach and work with in my .C file?

- What is happening inside the brackets after

IOobjects 
( 
    "Tave" 
    ... 
),

?

- Do I need to #include any libraries or namespaces for this to work? I created a blank functionObject using foamNewFunctionObject so I have minimum libraries included.


I would be very thankful for any help on this.

Cheers,
David

[gcengineer]

FWIW. In OFv1906,

//- Loop across all elements in \a list
// \par Usage
// \code
// forAll(anyList, i)
// {
//      statements;
// }
// \endcode
// \sa forAllReverse
#define forAll(list, i) \
     for (Foam::label i=0; i<(list).size(); ++i)

Other variations of forAll -- forAllIters, forAllConstIters, forAllReverseIters, forAllConstReverseIters, forAllReverse, forAllIter, and forAllConstIter -- are also defined in stdFoam.H.