CFD Online Discussion Forums

CFD Online Discussion Forums (
-   OpenFOAM Running, Solving & CFD (
-   -   what do global and cumulative terms in continuity refer to exactly? (

immortality January 12, 2013 04:55

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

fumiya January 13, 2013 06:17

For the solvers of incompressible fluid, take a look at the


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

    scalar sumLocalContErr = runTime.deltaTValue()*

    scalar globalContErr = runTime.deltaTValue()*
    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.


immortality January 16, 2013 10:15

thanks fumiya
I cant grasp how the total continuity is case is compressible.
What does mean cumulative continuity error?
Any hint is accepted here!

All times are GMT -4. The time now is 11:49.