CFD Online Discussion Forums - Shear-Rate calculation

Hi everyone, I am trying to calculate the Shear rate, defined as the square root of the double dot product of the strain-rate tensor with itself. In order to do so I added the following lines of code to the createFields.H of the solver I am currently using:

Code:



Info<< "Reading field strainRate\n" << endl;

volScalarField strainRate

(

    IOobject

    (

        "strainRate",

        runTime.timeName(),

        mesh,

        IOobject::MUST_READ,

        IOobject::AUTO_WRITE

    ),

    1.41421356237*mag(symm(fvc::grad(U)))

);

The solver can be compiled and it run correctly, but the results of the new function are pratically 0 eveyrwhere. If I explore the folders corresponding to the time steps, what I found in the file is:

Code:

/*--------------------------------*- C++ -*----------------------------------*\

  =========                 |

  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox

   \\    /   O peration     | Website:  https://openfoam.org

    \\  /    A nd           | Version:  7

     \\/     M anipulation  |

\*---------------------------------------------------------------------------*/

FoamFile

{

    version     2.0;

    format      binary;

    class       volScalarField;

    location    "0.1";

    object      strainRate;

}

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //



dimensions      [0 0 -1 0 0 0 0];



internalField   uniform 0;



boundaryField

{

    leftWall

    {

        type            calculated;

        value           uniform 0;

    }

    rightWall

    {

        type            calculated;

        value           uniform 0;

    }

    lowerWall

    {

        type            calculated;

        value           uniform 0;

    }

    atmosphere

    {

        type            calculated;

        value           uniform 0;

    }

    defaultFaces

    {

        type            empty;

    }

}





// ************************************************************************* //

So it basically performs the computation on the initial velocity field (U=0 everywhere).
Can someone help me?

Thanks in advance.