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## Turbulent quantities

• Turbulence parameters are set in file turbulenceProperties in directory constant
• Print the file on the screen:
# cat \$FOAM_RUN /pitzDaily/constant/turbulenceProperties
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  dev                                   |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
version     2.0;
format      ascii;
class       dictionary;
location    "constant";
object      turbulenceProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

simulationType RAS;

RAS
{
// Tested with kEpsilon, realizableKE, kOmega, kOmegaSST, v2f,
RASModel        kEpsilon;

turbulence      on;

printCoeffs     on;
}

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


• Parameter symulationType sets RAS, which stands for Reynolds averaged Navier-Stokes.
• RAS subdictionary sums up all necessary settings for RAS.
• RASModel is set to . Other possibilities are summed up in the commentary.
• Parameter turbulence can switch turbulence on or off (on/off )
• Parameter printCoeffs means the turbulence model coefficients are to be printed in standard output to the screen, when solver starts

Selecting RAS turbulence model kEpsilon
RAS
{
RASModel        kEpsilon;
turbulence      on;
printCoeffs     on;
Cmu             0.09;
C1              1.44;
C2              1.92;
C3              0;
sigmak          1;
sigmaEps        1.3;
}

• Parameter kEpsilonCoeffs is optional, and can change default turbulence model coefficients
•

## Potential of a homogeneous gravitational field

A homogeneous gravitational field is characterized by a constant vector field , the well known gravitational acceleration. Let us consider some volume or vessel filled with an incompressible fluid of density . The gravitational field exerts a force on the fluid. Its force density is given by the following well known formula

It is a simple task to  potential to (). Let us remind, a potential (if it exists) of some given force field is defined as a certain function satisfying the following equation

We can see that to the given by () there exists a potential, let us denote it by , stating
where is a constant of integration3.3 and is a position vector3.4.