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Curvature of the interface using interFoam

Hi all,

I am using interFoam to simulate multiphase flow in different geometries and I tried to write a little piece of code (writeCurvature.C that i call as a post processing) to calculate the curvature of the interface following the same method that openFoam normally use in the VOF method. (the calculations that i have done are identical to those in interfaceProperties.C). The problem is that I get strange result. I expected to find high values near the interface and values close to zero in the bulk but it is not!

i attached 2 jpg. one is the colour plot of alpha1 and the other one is the colour plot of the curvature that i got.
Any suggestion?

thanks
andrea

someone who has any idea why I find this curvature?
These are the calculations I've done:

Code:



reading alpha1 first

then



// now calc the gradients

        volVectorField gradAlpha1 = fvc::grad(alpha1);



         Info<< "Writing gradAlpha1 to " << gradAlpha1.name() << " in "

             << runTime.timeName() << endl;



         gradAlpha1.write();





         // Interpolated face-gradient of alpha

        surfaceVectorField gradAlphaf = fvc::interpolate(gradAlpha1);





        dimensionedScalar deltaN_ =  1e-8/pow(average(alpha1.mesh().V()), 1.0/3.0);





        // Face unit interface normal

        surfaceVectorField nHatfv = gradAlphaf/(mag(gradAlphaf) + deltaN_);





        // Face unit interface normal flux

        const surfaceVectorField& Sf = mesh.Sf();

        surfaceScalarField nHatf_ = nHatfv & Sf;



        volScalarField curvature

        (

         IOobject

         (

          "Curvature",

          runTime.timeName(),

          mesh,

          IOobject::NO_READ,

          IOobject::AUTO_WRITE

          ),



         -fvc::div(nHatf_)



         );

The thing that I can not understand is if I'm doing something wrong or if it is normal to find such values

thanks
andrea