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Old   June 18, 2013, 06:18
Default AlphaCourantNo code
  #1
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Hi to all
I want to know how is calculated AlphaCourantNo so I look for the code and I find this lines.

if (mesh.nInternalFaces())
{
scalarField sumPhi
(
pos(alpha1 - 0.01)*pos(0.99 - alpha1)
*fvc::surfaceSum(mag(phi))().internalField()
);

alphaCoNum = 0.5*gMax(sumPhi/mesh.V().field())*runTime.deltaTValue();

}

My understanding of this piece of code is that for each cell it sums the face flux magnitudes, divides it by the cell volume and multiplies it with deltaT/2. The maximum over all cells is then the Courant number.
But I don't understand the meaning of this term:

pos(alpha1 - 0.01)*pos(0.99 - alpha1)

Anyone kwon the meaning of it?
Thank to all
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Old   May 25, 2014, 10:07
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  #2
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enzhen zhang
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Location: Shanghai,China
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Quote:
Originally Posted by giack View Post
Hi to all
I want to know how is calculated AlphaCourantNo so I look for the code and I find this lines.

if (mesh.nInternalFaces())
{
scalarField sumPhi
(
pos(alpha1 - 0.01)*pos(0.99 - alpha1)
*fvc::surfaceSum(mag(phi))().internalField()
);

alphaCoNum = 0.5*gMax(sumPhi/mesh.V().field())*runTime.deltaTValue();

}

My understanding of this piece of code is that for each cell it sums the face flux magnitudes, divides it by the cell volume and multiplies it with deltaT/2. The maximum over all cells is then the Courant number.
But I don't understand the meaning of this term:

pos(alpha1 - 0.01)*pos(0.99 - alpha1)

Anyone kwon the meaning of it?
Thank to all
I have the same question.Does anyone know the meaning?
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Old   May 30, 2014, 09:47
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  #3
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Daniel Deising
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Hi enzhen,
this line
Code:
pos(alpha1 - 0.01)*pos(0.99 - alpha1)
gives you all cells where the volumetric phase fraction takes
values between 0.01 and 0.99.
And this piece of code
Code:
0.5*gMax(sumPhi/mesh.V().field())*runTime.deltaTValue();
is the definition of the Courant number in multiple dimensions,
assuming that the calculated velocity field is divergence free.

So as a result, you obtain a Courant number in the interfacial area.

Hope this helps,

Best,
Daniel
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Old   May 31, 2014, 13:58
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enzhen zhang
Join Date: Dec 2013
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Quote:
Originally Posted by danieldeising View Post
Hi enzhen,
this line
Code:
pos(alpha1 - 0.01)*pos(0.99 - alpha1)
gives you all cells where the volumetric phase fraction takes
values between 0.01 and 0.99.
And this piece of code
Code:
0.5*gMax(sumPhi/mesh.V().field())*runTime.deltaTValue();
is the definition of the Courant number in multiple dimensions,
assuming that the calculated velocity field is divergence free.

So as a result, you obtain a Courant number in the interfacial area.

Hope this helps,

Best,
Daniel
thanks ~that does help
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