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what do global and cumulative terms in continuity refer to exactly?

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Old   January 12, 2013, 04:55
Default what do global and cumulative terms in continuity refer to exactly?
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Ehsan
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at results there are 3 types of residuals of continuity equation.whats the definition of them and difference?if cumulative and or global be negative whats wrong in the problem?
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Old   January 13, 2013, 06:17
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Fumiya Nozaki
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For the solvers of incompressible fluid, take a look at the
src/finiteVolume/cfdTools/incompressible/continuityErrs.H:

Code:
    volScalarField contErr(fvc::div(phi));

    scalar sumLocalContErr = runTime.deltaTValue()*
        mag(contErr)().weightedAverage(mesh.V()).value();

    scalar globalContErr = runTime.deltaTValue()*
        contErr.weightedAverage(mesh.V()).value();
    cumulativeContErr += globalContErr;

    Info<< "time step continuity errors : sum local = " << sumLocalContErr
        << ", global = " << globalContErr
        << ", cumulative = " << cumulativeContErr
        << endl;
From the above definitions, the difference between the local and global
continuity error is whether the magnitude of divergence is taken or not.
The "local" error is a measure of the continuity of each cell and the
"global" error represents the continuity in the whole computational domain.
If the global error converges to zero, I think the negative value is of no matter.

I have no idea about the importance of considering the cumulative error.

Fumiya
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Old   January 16, 2013, 10:15
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thanks fumiya
I cant grasp how the total continuity is calculated.my case is compressible.
What does mean cumulative continuity error?
Any hint is accepted here!
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