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Problem with mass flux calculation in libsimpleFunctionObjects.so

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Old   June 24, 2017, 15:02
Default Problem with mass flux calculation in libsimpleFunctionObjects.so
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Hello,


i want to check the mass balance for multiphase cases while running the solver multiphaseEulerFoam. Ideally i want to create an output that calculates the mass balance for all phases e.g. for water and a secondary air phase. So far the closest i got to that is using

Code:
functions
{

    MassflowInlet
  {
    type                    faceSource;
    functionObjectLibs      ("libfieldFunctionObjects.so");
    enabled                 true;
    outputControl           timeStep;
    outputInterval          1;
    outputControlMode       timeStep;
    log                        true;
    valueOutput          false;
    source                  patch;
    sourceName           outlet;
    operation               sum;
     
fields
                (
      phi.water
      phi.air
                );
  }
}
to ControlDict and calculating the imbalance by hand. The issue here is that the mass flux on outlet is incorrect. In an early time step there is no secondary phase on the outlet, so therefore the flux must be ZERO but it isn't. It's pretty much the inlet divided by two. I have in total one inlet and two outlets. Getting a NON zero flux for the secondary phase doesn't make sense to me, there is not yet air on the outlet, why does OpenFoam have flux there? The alpha values area averaged correctly on the outlets. What am i missing here?

Also, is there a possibilty to check the overall mass balance with a function object or do i need to calcualte it by hand for each time step?

Thanks!!
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Old   June 24, 2017, 15:36
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Ok, i found that phi in incompressible solvers is m^3/s and so i guess, to get the mass flux i have to calculate by hand with average alpha on outlet face and the density of the phase.
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