[saeed jamshidi]

Hello Foamers,
Hope you are doing well.

I have come across another question in the realm of openfoam tutorials. Would you please tell me what is the role of DMD utility in openfoam?
I have seen them in the pimpleFoam/laminar/cylinder2D, and attached one of them:

// -*- C++ -*-

stdmd01
{
    // Mandatory entries (unmodifiable)
    type                DMD;
    libs                (fieldFunctionObjects);
    DMDModel            STDMD;
    field               U;

    // Optional entries (unmodifiable)
    /* patch               <patchName>; */

    // Conditional mandatory entries (runtime modifiable)

        // Option-1
        /* interval            5.5; */

        // Option-2
        /* executeInterval     10; */

    // Optional entries (runtime modifiable)
    /* modeSorter          firstSnapshot; */
    /* nGramSchmidt        5; */
    /* maxRank             50; */
    /* nModes              50; */
    /* fMin                0; */
    /* fMax                1000000000; */

    // Optional entries (runtime modifiable, yet not recommended)
    /* minBasis            0.00000001; */
    /* minEVal             0.00000001; */
    /* sortLimiter         500.0; */


    // Optional (inherited) entries
    region          region0;
    enabled         true;
    log             true;
    timeStart       10;
    timeEnd         1000;
    executeControl  timeStep;
    executeInterval 10;
    writeControl    onEnd;
    writeInterval   1;
}


// ************************************************************************* //

Regards

[Tobermory]

https://www.openfoam.com/documentati...D.html#details

[saeed jamshidi]

Tobermory thanks for the reply.

I red this source before, and I couldn't understand what exactly is the application of that!

Could you kindly tell me based on your experience?
Tnx.

[Tobermory]

If you want to dive into the detail, try: https://www.youtube.com/watch?v=sQvrK8AGCAo, or the wiki page on DMD.

In simple terms, for this application, it is a method of identifying coherent structures, i.e. eddies shed off the cylinder. Enjoy.

[Gang Wang]

Dear Foamers!

Have you tried with STDMD in the latest OF2312? I wonder the criterion for selecting the executeInterval or so-called stdmdInterval, which is also the STDMD time-step size. It equals the executeInterval*(current time-step of the simulation). But, would the different choices of stdmdIntervals affect the DMD modes?

Regards,
Gang