[Ahyar]

I was working on a multiphase case which has 3 phases, air2, air2, and water. I create 2 population balance system for each air1 and air2 phase. this is my

phaseProperties

in constant directory.

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  9
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    format      ascii;
    class       dictionary;
    object      phaseProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

type populationBalanceMultiphaseSystem;

phases (air1 air2 water);

populationBalances (air3 air4);

air1
{
    type            pureIsothermalPhaseModel;

    diameterModel   velocityGroup;

    velocityGroupCoeffs
    {
        populationBalance    air3;

        shapeModel           spherical;

        sizeGroups
        (
            f1 {dSph  4e-3; value 0.8;}
            f2 {dSph  5e-3; value 0.1;}
            f3 {dSph  6e-3; value 0.1;}
        );
    }

    residualAlpha   1e-6;
}

air2
{
    type            pureIsothermalPhaseModel;

    diameterModel   velocityGroup;

    velocityGroupCoeffs
    {
        populationBalance    air4;

        shapeModel           spherical;

        sizeGroups
        (
            f4 {dSph  7e-3; value 0.3;}
            f5 {dSph  8e-3; value 0.3;}
            f6 {dSph  9e-3; value 0.4;}
        );
    }

    residualAlpha   1e-6;
}

water
{
    type            pureIsothermalPhaseModel;

    diameterModel   constant;

    constantCoeffs
    {
        d               1e-3;
    }

    residualAlpha   1e-6;
}

populationBalanceCoeffs
{
    air3
    {
        continuousPhase water;

        coalescenceModels
        (
            LehrMilliesMewes{}
        );

        binaryBreakupModels
        (
            LehrMilliesMewes{}
        );

        breakupModels
        ();

        driftModels
        (
            densityChange{}
        );

        nucleationModels
        ();
    }
    air4
    {
        continuousPhase water;

        coalescenceModels
        (
            LehrMilliesMewes{}
        );

        binaryBreakupModels
        (
            LehrMilliesMewes{}
        );

        breakupModels
        ();

        driftModels
        (
            densityChange{}
        );

        nucleationModels
        ();
    }
}

blending
{
    default
    {
        type            none;
        continuousPhase water;
    }
}

surfaceTension
(
    (air1 and water)
    {
        type            constant;
        sigma           0.083;
    }

    (air2 and water)
    {
        type            constant;
        sigma           0.083;
    }
);

interfaceCompression
();

aspectRatio
(
    (air1 in water)
    {
        type            Wellek;
    }

    (air2 in water)
    {
        type            Wellek;
    }
);

drag
(
    (air1 in water)
    {
        type            IshiiZuber;

        residualRe      1e-3;
        swarmCorrection
        {
            type        none;
        }
    }

    (air2 in water)
    {
        type            IshiiZuber;

        residualRe      1e-3;
        swarmCorrection
        {
            type        none;
        }
    }
);

virtualMass
(
    (air1 in water)
    {
        type            constantCoefficient;
        Cvm             0.5;
    }

    (air2 in water)
    {
        type            constantCoefficient;
        Cvm             0.5;
    }
);

heatTransfer
();

phaseTransfer
();

lift
(
    (air1 in water)
    {
        type            wallDamped;

        wallDamping
        {
            type        cosine;
            Cd          3.0;
        }

        lift
        {
            type        Tomiyama;

            swarmCorrection
            {
                type    none;
            }
        }
    }

    (air2 in water)
    {
        type            wallDamped;

        wallDamping
        {
            type        cosine;
            Cd          3.0;
        }

        lift
        {
            type        Tomiyama;

            swarmCorrection
            {
                type    none;
            }
        }
    }
);

wallLubrication
(
    (air1 in water)
    {
        type            Antal;
        Cw1             -0.01;
        Cw2             0.05;
    }

    (air2 in water)
    {
        type            Antal;
        Cw1             -0.01;
        Cw2             0.05;
    }
);

turbulentDispersion
(
    (air1 in water)
    {
        type            Burns;
        sigma           0.9;
    }

    (air2 in water)
    {
        type            Burns;
        sigma           0.9;
    }
);

// ************************************************************************* //

Then I tried to create the third population balance system that calculate the aggregate of two phases air1 and air2, but how to achieve this? i tried to add the populationbalance on air1 to be like this below

air1
{
    type            pureIsothermalPhaseModel;

    diameterModel   velocityGroup;

    velocityGroupCoeffs
    {
        populationBalance    (air3 and air4);

        shapeModel           spherical;

        sizeGroups
        (
            f1 {dSph  4e-3; value 0.8;}
            f2 {dSph  5e-3; value 0.1;}
            f3 {dSph  6e-3; value 0.1;}
        );
    }

    residualAlpha   1e-6;
}

but it didn't work, says that the populationBalance only take word input and no punctuation like "(" can openfoam create aggregate population balance system? thanks in advance