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Calculating fluctuation flux (Reynolds flux) of scalar in LES?

Hi FOAMer! I am using LES to simulate the scalar mixing in wall-bounded turbulent flow. The LES could calculate the transient velocity field U and scalar field s. With the fieldAverage function, the time-averaged value UMean and sMean could also be obtained.
Now I want to output the time-avearged flux and fluctuation flux of scalar, namely the <Us> and <U's'>, which requires to calculate the expression U*s and (U-UMean)*(s-sMean) and pass the result to fieldAverage function.
After searching through the forum, maybe the easiest way is to impose coded functionObject in controlDict file. I adapt the code in thread

HTML Code:

https://www.cfd-online.com/Forums/openfoam-post-processing/219817-fluctuating-component-scalar-quantity.html

to my case, but the simulation aborted in the middle of the process and the error shows:

Quote:

new cannot satisfy memory request.
This does not necessarily mean you have run out of virtual memory.
It could be due to a stack violation caused by e.g. bad use of pointers or an out of date shared library

BTW, I use the parallel computation on HPC.
Does anyone know the way to handle this, or any other workaround?

For quick reference, I post the adapted code below, in which the flux1 represents the product of U and s.

Code:

fluctuation_flux1

        {

                type                        coded;

                libs                        ("libutilityFunctionObjects.so");

                enabled                true;

                timeStart                74;

                timeEnd                200;

                writeControl        adjustableRunTime;

                writeInterval        200;

                name                fluctuation_flux1;

                

                codeExecute

                #{

                        const volVectorField& U = 

                        mesh().lookupObject<volVectorField>("U");                

                        const volScalarField& s = 

                        mesh().lookupObject<volScalarField>("s");                

                        

                        obr_.store

                        (

                                new        volVectorField        

                                (

                                        IOobject

                                        (

                                                "flux1",

                                                obr_.time().timeName(),

                                                obr_,

                                                IOobject::NO_READ,

                                                IOobject::AUTO_WRITE

                                        ),

                                        U*s

                                )

                        );

                        const volVectorField& flux1 = 

                        obr_.lookupObject<volVectorField>("flux1");

                #};

        }

Also the fieldAverage function to average the flux1 in time:

Code:

fieldAverage1

    {

      type                        fieldAverage;

      functionObjectLibs   ( "libfieldFunctionObjects.so" );

      resetOnRestart         true;

      resetOnOutput         false;

      startTime                75;                 

      endTime                 200;                 

      writeControl            adjustableRunTime;

      writeInterval           200;

      

      fields

      (

            flux1

           {

            mean              on;

            prime2Mean    on;

            base               time;          

           }

      ); 

    }