[cojua8]

Hello,

I'm trying to calculate the turbulence intensity of my simulation.

the formula for this is:

or, in terms of openFoam:

So, my idea is to use the fieldAverage function:

fieldAverage1
    {
        type                fieldAverage;
        libs                ("libfieldFunctionObjects.so");

        writeControl        writeTime;

        restartOnRestart    true;
        restartOnOutput     false;
        periodicRestart     true;
        restartPeriod       5;

        fields
        (
            U
            {
                mean            on;
                prime2Mean      off;
                base            time;
            }
         
        );
    }

and then create a codedFunction which creates a new turbulenceIntensity field and adds it to registry:

turbulenceIntensity
    {
        functionObjectLibs ("libutilityFunctionObjects.so");
        type coded;
        writeControl writeTime;
        name writeTurbulenceIntensity;
        codeWrite
        #{
            const volVectorField& U = mesh().lookupObject<volVectorField>("U");
            const volVectorField& Umean =
                mesh().lookupObject<volVectorField>("Umean");

            volScalarField turbulenceIntensity
            (
                IOobject
                (
                    "turbulenceIntensity",
                    mesh().time().timeName(),
                    mesh(),
                    IOobject::NO_READ,
                    IOobject::AUTO_WRITE
                ),
                sqrt(1.0/3.0)*mag(U-Umean)/mag(Umean)
            );
            turbulenceIntensity.checkIn();
        #};
    }

then, I want to calculate the mean of this field over time, adding the field to the fieldAverage function.

...
turbulenceIntensity
{
    mean            on;
    prime2Mean      off;
    base            time;
}
...

but this does not seem to work, but also there are no errors.

How can I do this?

[em17]

Hi,

OpenFOAM already has a postprocessing function for turbulence intensity. You can include this in your controlDict to write out the TI field during run time - simply include #includeFunc turbulenceIntensity in your functions section.

Emily