[studente]

Dear Foamers,

I'm new to OpenFoam and still learning. I have a case where freestream flows over a rotating VAWT (vertical axis wind turbine). I'm using k--SST turbulence model, so I got to find first which initial value of k and in folder 0.

Here below is my calculation and formulas I got from some sources, to calculate k and around airfoil:

= freestream velocity
= Tip-Speed-Ratio
= chord length
= density of air
= dynamic viscosity

#Calculation of Reynoldsnumber Re
= =

#Calculation of Turbulence intensity I
= 0.16 *

#Calculation of turbulent length scale
=

= * c

#Calculation of turbulent kinetic energy k
= *

#Calculation of specific dissipation rate
=

but here's the thing, those formulas above apply only for calculation on airfoil. Assuming that our freestream flows through a wind tunnel (a duct). That means, that we can calculate the Reynoldsnumber on inlet with this formula below:

=

with is hydraulic diameter of the windtunnel

After I got the , then I can calculate , then I can calculate , and end up getting and . The question is, how to calculate them? We can't use the first formulas above to calculate and on inlet, InternalField, and topBottom, since it applied only for airfoil. And here actually I'm not really sure, if my approach is correct as well.

Otherwise I put my code for and below. The initial values that I got there is from the formulas for airfoil, without consideration to calculate and on inlet, InternalField , and topBottom. I just go through all of them and put the same values as it were on airfoil. I name my airfoils as lowerBlade and upperBlade in my code.

I really appreciate any helps and comments! Thanks!

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2006                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      k;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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


internalField   uniform 0.11637565440834571; // k = (3/2) * U_inf^2 * I^2

boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform 0.11637565440834571;
    }
    outlet
    {
        type            zeroGradient;
    }
    topBottom
    {
        type            kqRWallFunction;
        value           uniform 0.11637565440834571;
    }
    ami00
    {
        type            cyclicAMI;
        value           uniform 0.11637565440834571;
    }
    ami01
    {
        type            cyclicAMI;
        value           uniform 0.11637565440834571;
    }
    lowerBlade
    {
        type            kqRWallFunction;
        value           $internalField;
    }
    upperBlade
    {
        type            kqRWallFunction;
        value           $internalField;
    }
    frontAndBack
    {
        type            empty;
    }
}


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

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2006                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      omega;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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


internalField   uniform 14.770814500415696; // omega = k^(1/2) / l

boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform 14.770814500415696;
    }
    outlet
    {
        type            zeroGradient;
    }
    topBottom
    {
        type            omegaWallFunction;
        value           uniform 14.770814500415696;
    }
    ami00
    {
        type            cyclicAMI;
        value           uniform 14.770814500415696;
    }
    ami01
    {
        type            cyclicAMI;
        value           uniform 14.770814500415696;
    }
    lowerBlade
    {
        type            omegaWallFunction;
        value           $internalField;
    }
    upperBlade
    {
        type            omegaWallFunction;
        value           $internalField;
    }
    frontAndBack
    {
        type            empty;
    }
}


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