[calim_cfd]

Originally Posted by Esther Jin

Hello, I am doing LES turbulence simulation using OpenFOAM3.0.1, and have some questions about the turbulenceProperties in the constant folder of pitzDaily in tutorials, I don't understand what LESdelta means, is it related to filter width?

simulationType  LES;

LES
{
    LESModel        dynamicKEqn;

    turbulence      on;

    printCoeffs     on;

    delta           cubeRootVol;

    dynamicKEqnCoeffs
    {
        filter simple;
    }

    cubeRootVolCoeffs
    {
        deltaCoeff      1;
    }

    PrandtlCoeffs
    {
        delta           cubeRootVol;
        cubeRootVolCoeffs
        {
            deltaCoeff      1;
        }

        smoothCoeffs
        {
            delta           cubeRootVol;
            cubeRootVolCoeffs
            {
                deltaCoeff      1;
            }

            maxDeltaRatio   1.1;
        }

        Cdelta          0.158;
    }

    vanDriestCoeffs
    {
        delta           cubeRootVol;
        cubeRootVolCoeffs
        {
            deltaCoeff      1;
        }

        smoothCoeffs
        {
            delta           cubeRootVol;
            cubeRootVolCoeffs
            {
                deltaCoeff      1;
            }

            maxDeltaRatio   1.1;
        }

        Aplus           26;
        Cdelta          0.158;
    }

    smoothCoeffs
    {
        delta           cubeRootVol;
        cubeRootVolCoeffs
        {
            deltaCoeff      1;
        }

        maxDeltaRatio   1.1;
    }
}

If I choose VanDriest as Delta, in log file it shows the LES delta type selected twice,

PHP Code:

PIMPLE: Operating solver in PISO modeReading field pReading field UReading/calculating face flux field phiSelecting incompressible transport model NewtonianSelecting turbulence model type LESSelecting LES turbulence model SmagorinskySelecting LES delta type vanDriestSelecting LES delta type cubeRootVolSmagorinskyCoeffs{    Ck              0.094;    Ce              1.048;} 


I also want to use Van Driest damping function, but I am so confused with these LES deltas and coefficients. Could anyone please explain me about these parameters if you have experience with LES turbulent flow simulation?

Thank you in advance!

Best regards,
Esther

Hi Esther.

This reply isn't a reply because i'm not an expert in LES, though i've read a few things about. And from my readings, i believe you should read get more familiar with the concept of filtering and the available turbulence models in OF. The parameters may change from model to model.

It is just a suggestion because you may bump into errors and not be able to debug them because it is a "dimensioning issue", even thou OF is now more user friendly :P

You may try these books along with a few dozen papers

https://www.amazon.com/Turbulent-Flo...urbulence+pope
https://mitpress.mit.edu/books/first-course-turbulence

Sorry i could not help you

[anishtain4]

First it's odd that you have "delta cubeRootVol;" in your turbulenceProperties and it is using vanDriest! It usually should be "delta vanDries;".
You can have a good read about the delta and wall functions of LES simulation in OpenFOAM in this topic:
http://www.cfd-online.com/Forums/ope...nel-flows.html