[nguyenduclong777]

Dear Openfoamers,

I would like to ask for your help

I am using LES Smagorinsky model and interFoam to modelling 3D turbulent dynamic of a spillway. It run smoothly and stable. However, for calibration, which parameter should I adjust?

1. I adjusted the roughness of the model by creating a finer net. As a result, the model run very slowly because of enormous cells (3.8 million cells with a vertical cell size 60*mm). Meanwhile. the previous model consists of 400,000 Cells only with the vertical cell size 40cm

2. Then, I tried to use nutkRoughWallFunction in Nut file. It was defined as follow:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: 5 |
| \\ / A nd | Web: www.OpenFOAM.org |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0";
object nut;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [0 2 -1 0 0 0 0];

internalField uniform 1e-11;

boundaryField
{
inlet
{
type zeroGradient;
}
outlet
{
type zeroGradient;
}

top
{
type zeroGradient;
}

rinne
{
type nutkRoughWallFunction;
Ks uniform 0.006;
Cs uniform 0.5;
value $internalField;
}

}


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


Note : Ks=(25.6/Kst)^6 = (25.6/60)^6 = 0.006 ( equivalent Concrete Wall) ;
Kst: Strickler roughness = 1/n (n: Manning coefficient)

The model was running a few minutes and was crashed due to a large Courant number, although the time step was very fine (10^-11). I also let the interFoam change the time step automatically but It didn't work

What should I do to calibrate the model?

Here is the link to model:

https://drive.google.com/drive/folde...usp=share_link


Many thanks in advance
Best regards,
Steve