[Mirage]

Dear OF-Users,

I am running an LES simulation and I have some questions concerning the time averaging in OpenFOAM 3.0 for a incompressible solver: pisoFoam.

I start to average my field after 10 FTT (flow thought times). I observed that in the first averaged FTT huge oscillations occur, when i monitor pMean over the time in one point (attachment pMeanVsTime_point1.png ). I think that these oscillations will effect the result accuracy even after 30 FTT . Is that correct?

So I took my field result after 20 FTT and deleted all the averaged variables (pMean, UMean, ...) and the field averaging properties in the uniform folder and I started to average from 20 FTT. However is this case huge oscillations occur also! (attachment pMeanVsTime_point1_Avg20.png )

As you can see the sign of pMean is changing after the new averaging... is that wrong?
Are huge Amplitude effecting the quality of results?
Why do they occur in the beginning of the averaging?
How can i avoid this huge oscillations?

here is how I do the averaging in the controlDict:

functions
{ 
    fieldAverage1
    {
        type            fieldAverage;
        functionObjectLibs ("libfieldFunctionObjects.so");
        enabled         true;
        outputControl   outputTime;

        fields
        (
            U

            {
                mean        on;
                prime2Mean  on;
                base        time;
            }

            p
            {
                mean        on;
                prime2Mean  on;
                base        time;
            } 
                T
            {
                mean        on;
                prime2Mean  on;
                base        time;
            } 
        );
    }

I appreciate any help !

[The_Kaiser]

I have a similar problem, however with an IDDES. If anybody could give an advice, I would be grateful