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Which boundary condition should be choose for a uniform field

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Old   May 2, 2008, 08:22
Default Dear group These days, I h
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Dear group

These days, I have been trying to implement population balance equation into twoPhaseEulerFoam Solver. But some strange things confused me when I change the type of the diameter of bubbles.( from the dimensionedScalar to volScalarField)

Two different methods were used to set the initial values of diameter. To compare the computational results with those from the original codes, the diameter remained the same over the whole domain within the simulation time.

the first method:
read the diameter (uniform in the domain),and set them in the constructor of the phaseModel

d_
(
IOobject
(
"d" +phaseName,
mesh.time().timeName(),
mesh,
IOobject::NO_READ, //NO READ
IOobject::AUTO_WRITE
),
mesh,
dimensionedScalar(dict_.lookup("d"))
)

the second method:
read it from the IOobject
d_
(
IOobject
(
"d" +phaseName,
mesh.time().timeName(),
mesh,
IOobject::MUST_READ, //MUST READ
IOobject::AUTO_WRITE
),
mesh
)

the file of da (a is phase name)
FoamFile
{
version 2.0;
format ascii;

root "";
case "";
instance "";
local "";

class volScalarField;
object da;
}

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


dimensions [0 1 0 0 0 0 0];

internalField uniform 0.003;
boundaryField
{
inlet
{
type calculated;
value uniform 0.003;
}

outlet
{
type calculated;
value uniform 0.003;


}

walls
{
type calculated;
value uniform 0.003;

}

defaultFaces
{
type empty;
}
}

computational results from the first method is totally the same as the original code, but not with the second methods, even though with some other boundary conditions, fixedvalue, zeroGrient.

Why? what is the difference between them, which boundary should be used?

Would you give me some suggestion?

Thanks, su junwei
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