[Chikiton]

Hi foamers,
I'm doing a multhiphase task with 3 phases using multiphaseInterFoam and i want to get volume integral of the some variables and of their multiplication, for example, mass of one phase.
in the controlDict file, I want to use a function to calculate the integral for the quantity ( rho*alpha.water) during the whole calculation.
I has found this topic - integrate several fields , but in last version OpenFOAM some functions of swak4foam was included in the OpenFOAM.
I want use smth like this (code from link above)

functions
{
    makeMagU {
       type expressionField;
         functionObjectLibs
        (
            "libswakFunctionObjects.so"
        );      autowrite false;
       fieldName magU;
       expression "mag(U)";
    }
    temp_average
    {
        type volumeAverage;
        functionObjectLibs
        (
            "libsimpleFunctionObjects.so"
        );
        verbose true;
        fields (magU);
    }
}

but I don't know how to implement this in version 1912. Maybe anybody knows. Please help. Thanks.

[Chikiton]

Update:
I saw this topic : New Documentation: OpenFOAM Expressions (reImpl of swak4Foam of Bernhard Gschaider)
But don't know how to use this documentation.
And further. saw this code to determine the field:

compute_ptot
            {
                type expressionField;
                outputControl timeStep;
                outputInterval 1;
                fieldName ptot;
                expression "p + 0.5*magSqr(U)";
                autowrite false;        
            }

but again , this function from swak4foam, and how it use in new versions OF?

[HPE]

Hi,

If you need to compute the above expression only, OpenFOAM has derivedFields function object with which you can compute "pTotal".

Hope this helps.

[olesen]

This is indeed one of the open points but the emphasis would actually be more on supporting expressions for surfaceFieldValue since this is where people might need to define some "weird" definition to evaluate. However, one of the constraints would is access to arbitrary fields. For patch types this is reasonably straight-forward, for faceZones it can mostly work, but also gets a bit hit-and-miss due to the face orientations, for sampled surfaces and registered surfaces it seems to be out-of-scope since it is just trying to do far too much.


For simple volume field generation, using one of the predefined one (as another poster suggested), or whip up a tiny coded function object to do the same probably makes the most sense.

[Chikiton]

thanks for replies!!! I found answers in this thread - integrate multiplication of fields