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Old   April 5, 2011, 07:59
Default solidParticleFoam reflection?
Andrew Ryan
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Dear Foamers

Looking at solidParticleFoam I didn't understand what the code in hitWallPatch (in solidParticle.C) is supposed to do, it looks like it just inverts the direction of the particle??

    vector nw = wpp.faceAreas()[wpp.whichFace(face())];
    nw /= mag(nw);

    scalar Un = U_ & nw;
    vector Ut = U_ - Un*nw;

    if (Un > 0)
        U_ -= (1.0 + td.spc().e())*Un*nw;

    U_ -= td.spc().mu()*Ut;
Anyways I just replaced it a formula for specular reflection.

    vector n = wpp.faceAreas()[wpp.whichFace(face())];
    n /= mag(n);
    U_ -= 2 * (U_ & n) * n;
The result now looks much better in paraview.
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Old   April 18, 2011, 04:02
Sylvain Aguinaga
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Hi Andrew,

I think that the way the reflection is implemented in OpenFOAM takes into account:
-the decrease of the normal velocity due to inelastic rebound, using the energy loss coefficient "e"
-the decrease of the tangential velocity due to the friction of the particle with the wall, using the coefficient mu

I think that if you take mu=0 (no friction) and e=1(perfect elastic rebound without energy loss) your formulation is the same as the one implemented in OpenFOAM. Looks like anyway…

If you specify e=1 and mu=0, the results are very different between your implementation and the one used in OpenFOAM?
Hope it will be helpfull…

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