CFD Online Discussion Forums - source term that stays constant over outerCorrectors of pimple loop

Dear all,

My transient compressible flow calculation requires addition of random disturbances to the boundary layers of a nozzle at a particular location. The way I tried to do it is

1) create a cellSet of the boundary cells at the location.

2) Add random momentum source terms (disturbances) of the necessary magnitude using fvOptions active only at the aforementioned cellSet.

The issue:
For reasons I can't elaborate here, I need to use a pimple solver with 5 outerCorrector loops. I would like to keep my source term constant over all the 5 correctors. Unfortunately, when I tried to do so, I realized that fvOptions is called each time the U.Eqn is solved and it modifies the disturbances at each outer corrector step. My code for fvOptions is shared below

Code:

codedSource

{

    type            vectorCodedSource;

    selectionMode   cellSet;

    cellSet         boundaryLayerForce;



    fields           (U);

    name           disturbance;



    codeInclude

    #{

    #include "Random.H"

    # include "clock.H"

    #};

    

    codeCorrect

    #{

    #};



    codeAddSup

    #{

        const Time& time = mesh().time();

        Random rng(time.value());//Random rng(clock::getTime() + pid());

        vectorField& USource = eqn.source();

       

        // Start time

        const scalar startTime = -1.0;



        if (time.value() > startTime)

        {

             const labelList& cellIDs = cells();

            // Apply the source

            forAll(cellIDs, i)

            {

                label cellI = cellIDs[i];

                vector epsilon (1, 1, 1);

                epsilon.x() = -1.0 + 2.0*(rng.scalar01());

                epsilon.y() = -1.0 + 2.0*(rng.scalar01());

                epsilon.z() = 2.0*(-1.0 + 2.0*(rng.scalar01()));

               

                USource[cellI].x() =1e-4*508*epsilon.x();

                USource[cellI].y() =1e-4*508*epsilon.y();

                USource[cellI].z() = 1e-4*508*epsilon.z();

            };

        

        }

    #};



    codeSetValue

        #{

        #};

}



        {

As you can see the disturbances are scaled a fixed order of magnitude from a scalar (1e-04*508). These are then randomly weighed with a different random number between -2 and 2 in each cell.

The constant updating of the disturbances within a time step is not what I want and it leads to immediate blow up of the calculation.

My questions:
Is it possible to use fvOptions to add source terms that stay constant at a time step over all the outer correctors? It seems possible as fvOptions can access the time value.

Do I have to modify my solver in order to add disturbances and solve with a pimple loop?