CFD Online Discussion Forums - Read a field at different times

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Read a field at different times

Hi,

I want to create a post-processing utility, which traverses all time steps and compares the data with the data of all other time steps. So I end up with two nested loops traversing all time steps.

So, in pseudo code, it looks like this:

Code:

    // go over all time steps

    forAll(timeDirs, timeI)

    {

        runTime.setTime(timeDirs[timeI], timeI);

        

        // go over all time steps

        forAll(timeDirs, timeJ)

        {

            secTime.setTime(timeDirs[timeJ], timeJ);

            

            if (timeI == timeJ)

            {

                // easy

                recurrenceMatrixAlpha[timeI][timeJ] = 1;

            }

            else

            {

                // do stuff

            }

        }

    }

In the "// do stuff" section, I read the fields at the two different times. Right now, I call the constructor, like this:

Code:

volScalarField alpha1

(

    IOobject

    (

        "alpha.air",

        runTime.timeName(),

        mesh,

        IOobject::MUST_READ,

        IOobject::NO_WRITE

    ),

    mesh

);

volScalarField alpha2

(

    IOobject

    (

        "alpha.air",

        secTime.timeName(),

        mesh,

        IOobject::MUST_READ,

        IOobject::NO_WRITE

    ),

    mesh

);

I assume, that this might be done faster.

Is there a way to just read the field at the current time, like read()?

Hi Gerhard,

did you solve this already? I'm also interested...

best regards,
Shir

---- edit 2019-06-03:
seems to be the only way.

As of now, there are two ways to deal with this problem:

Either, we read a pair of fields for each combination of times
Or, we read the fields at all times, and then compare each combination of times

So,we can choose between

Reading a lot
Using a lot of memory

I ended up implementing the second variant.

I'm quite new to OpenFoam, so maybe there is a better answer but if you know the time you need to read, you can convert into a word with the right precision using the runTime.timeName(scalar time) function.

For example, in my solver there is:

Code:

word cTime(runTime.timeName(currentTime[i].value()));



pointScalarField potPhi1

        (

            IOobject

            (

                "Phi",

                cTime,

                externalPhiRegions[i],

                IOobject::MUST_READ,

                IOobject::NO_WRITE

            ),

            pMeshes[i]

        );

Code for writeAlpha2

Hi everyone,

I'd like to share my successful code for writing int_V(alpha2)dV = "volume of gas phase" to postProcessing/volumeIntegrate_volumeIntegral/0/alpha2.
It's written for foam-extend-4.0.

Can also be used for postProcessing of a parallel case via e.g.

mpirun -np $threads writeAlpha2 -parallel

Install:

extract tar.gz to
$WM_PROJECT_DIR/applications/utilities/postProcessing/miscellaneous/
and cd there and do "wmake".