[SarahLee]

Hi

I am trying to run a steady state simulation the wind flow around a building with a courtyard. The goal is to assess how well ventilated the courtyard is. We would like to check this with the mean age of air concept.

I have looked into the previous discussion on this topic, but don't find an answer. My simulation is running stable, the flow field is developing well, but the mean age of air is not plausible: increase from the inlet at 0 s, around the building appr. 100 s and at the outlet about 200 s. Inside the courtyard, the Age of air stays around 0-30 s, which is physical nonsense. There must be a problem with my boundary conditions, though they couldn't be much simpler.

solver: buoyantboussinesqsimplefoam

AoA:
walls, top, outlet = zeroGradient
inlet (wind) = fixedValue, value uniform 0


controlDict:

/*---------------------------------------------------------------------------*\
|=========                 |                                                  |
|\\      /   F ield        | OpenFOAM: The Open Source CFD Toolbox            |
| \\    /    O peration    | Version:  3.0.0                                  |
|  \\  /     A nd          | Web:      www.OpenFOAM.org                       |
|   \\/      M anipulation |                                                  |
\*---------------------------------------------------------------------------*/
// Exported by BIM HVACTool Version 2.0.0.200//

FoamFile
{
    version         3.0;
    format          ascii;
    class           dictionary;
    location        "system";
    object          controlDict;
}

application     buoyantBoussinesqSimpleFoam;

startFrom       startTime;

startTime       0;

stopAt          endTime;

endTime         4000;

deltaT          1;

writeControl    timeStep;

writeInterval   250;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression compressed;

timeFormat      general;

timePrecision   6;

runTimeModifiable true;

functions
{
    AoA
    {
        type            scalarTransport;
        functionObjectLibs
        (
            "libutilityFunctionObjects.dll"
        );

        outputControl   outputTime;
        active          true;
        autoSchemes     true;
        nCorr           0;
        D               0;
        resetOnStartUp  false;
        fvOptions
        {
            IncrementTime
            {
                type            scalarSemiImplicitSource;
                active          true;
                cellZone        Layers;
                scalarSemiImplicitSourceCoeffs
                {
                    volumeMode      specific;
                    selectionMode   all;
                    injectionRateSuSp
                    {
                        AoA             (1 0);
                    }

                }

            }

        }

    }

}

Any feedback is much appreciated!

[tian]

Hi,



try out the solver: AoAFoam. Use the AoA file and the latest steady state results. Run the unsteady for 3600 seconds. Then check out AoA again.



Bye

Tian

[HPE]

hope the following link can be helpful as well: Age of Air Function Object