[Rojj]

Hi,

I have added a function object to calculate the Age Of Air in OF4.1. SimpleFoam converges, but I have some doubt about the interpretation of the results.

I have based the implementation on this thread

Mean Age of Air

In my controlDict I have added the following function

AoA
{
    type    scalarTransport;
    functionObjectLibs ("libutilityFunctionObjects.so");
    enabled true;
    writeControl outputTime;
    log yes;
    nCorr 1;

    field AoA;
    active          true;
    autoSchemes     false;
    resetOnStartUp false;
    DT              1e-5;

    fvOptions
    {
        IncrementTime
        {
            type            scalarSemiImplicitSource;
            active          true;
            scalarSemiImplicitSourceCoeffs
            {
                selectionMode all;
                volumeMode  specific;
                injectionRateSuSp
                {
                    AoA       (1 0);
                }
            }
        }
    }
}

I have then added the following boundary condition

dimensions [ 0 0 1 0 0 0 0 ];

internalField uniform 0.0;   

boundaryField
{
  inlet
  {
    type fixedValue;
    value uniform 0;
  }
  outlet
  {
    type zeroGradient;
  }
.....

Modified fvSchemes and fvSolution accordingly with

div(phi,AoA) bounded Gauss upwind;

and

    AoA
    {
        solver           smoothSolver;
        smoother         GaussSeidel;
        tolerance        1e-08;
        relTol           0.1;
        nsweep                   1;
    }

The solution converges, but I am not really sure I get what it means. My understanding is:

• We inject some kind of tracer at each point of the domain
• We assign uniform zero as BC
• The value of AoA tells us how long, in average, it will take for the air in that point to be replaced by new air coming from the boundary (outside)
• This is why we assign uniform 0 at the boundary

Is this correct?
What does IncrementTime actually do?
Why AoA has unit of Time?
Why we inject 1 of tracer?

[HPE]

It took me three years to reflect on these questions (kidding)

(maybe not)

Age of Air Function Object