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zeroGradient vs fixedGradient vs mixedBC

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Old   November 7, 2013, 15:45
Default zeroGradient vs fixedGradient vs mixedBC
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I tried to make my own boundary condition, and discovered, that the mixed boundary condition does not behave as expected. With the following set, I thought it would work like 'zeroGradient' or 'fixedGradient' with gradient=0, but it does not. The Poisson equation for p does not converge ...

type mixed;
gradient 0;
value 0;
valueFraction 0;

Any hints? Mixed boundary condition is a mix of Dirichlet and a normal gradient?
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Old   November 8, 2013, 05:07
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I found the solution: As implemented now, the mixed boundary condition can not be used as purely gradient boundary condition (valueFraction = 0).

Quote:
//- Return true if this patch field fixes a value.
// Needed to check if a level has to be specified while solving
// Poissons equations.
virtual bool fixesValue() const
{
return true;
}

Last edited by dl6tud; November 8, 2013 at 11:39.
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