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Previous: Turbulent quantities Up: Computation set-up Next: Physical model set-up

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Initial and boundary conditions for turbulent quantities

  • Two-equation turbulence model $ k-\epsilon$ is used
  • Initial and boundary conditions for turbulent kinematic energy $ k$, TKE dissipation rate $ \epsilon$ and kinematic eddy viscosity $ \nu_t$ must be specified.
  • Configuration file for turbulent kinematic energy $ k$:
    # cat $FOAM_RUN /pitzDaily/0/k

     

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

internalField   uniform 0.375;

boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform 0.375;
    }
    outlet
    {
        type            zeroGradient;
    }
    upperWall
    {
        type            kqRWallFunction;
        value           uniform 0.375;
    }
    lowerWall
    {
        type            kqRWallFunction;
        value           uniform 0.375;
    }
    frontAndBack
    {
        type            empty;
    }
}
  • Physical dimensions of turbulent kinematic energy are: [0 2 -2 0 0 0 0] – $ m^{2}s^{-2}$
  • Initial condition: $ k_0 = 0.375$ (constant in whole domain)
  • $ k_{\infty} = 0.375$ at the inlet
  • Turbulent kinematic energy is extrapolated at the outlet
  • Wall functions are set at the walls
  • At the patch frontAndBack (front and back side of the channel) is defined boundary condition empty, i.e. flow is not solved in this direction (quazi 3D – 2D simulation)

     

  • Configuration file for TKE dissipation rate:
    # cat $FOAM_RUN /pitzDaily/0/epsilon

     

    dimensions      [0 2 -3 0 0 0 0];

internalField   uniform 14.855;

boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform 14.855;
    }
    outlet
    {
        type            zeroGradient;
    }
    upperWall
    {
        type           epsilonWallFunction;
        value           uniform 14.855;
    }
    lowerWall
    {
        type           epsilonWallFunction;
        value           uniform 14.855;
    }
    frontAndBack
    {
        type            empty;
    }
}
  • Physical dimensions of TKE dissipation rate are: [0 2 -3 0 0 0 0] – $ m^{2}s^{-3}$
  • Initial condition: $ \epsilon_0 = 14.855$ (constant in whole domain)
  • $ \epsilon_{\infty} = 14.855$ at the inlet
  • TKE dissipation rate is extrapolated at the outlet
  • Wall functions are set at the walls
  • At the patch frontAndBack (front and back side of the channel) there is defined boundary condition empty, i.e. flow is not solved in this direction (quazi 3D – 2D simulation)

     

  • Configuration file for kinematic eddy viscosity:
    # cat $FOAM_RUN /pitzDaily/0/nut

     

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

internalField   uniform 0;

boundaryField
{
    inlet
    {
        type            calculated;
        value           uniform 0;
    }
    outlet
    {
        type            calculated;
        value           uniform 0;
    }
    upperWall
    {
        type            nutkWallFunction;
        value           uniform 0;
    }
    lowerWall
    {
        type            nutkWallFunction;
        value           uniform 0;
    }
    frontAndBack
    {
        type            empty;
    }
}
  • Physical dimensions of kinematic eddy viscosity dissipation rate are: [0 2 -1 0 0 0 0] – $ m^{2}s^{-1}$
  • This file is included because of technical reasons. In fact, it contains no new information from physical point of view, $ \nu_t$ is calculated from $ k$ and $ \epsilon$. It is enough to say that all walls have to have Wall functions, frontAndBack is empty as before and other patches are of type calculated.
  • Other files in 0 directory are for other turbulence models and can be deleted.
  •  
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Previous: Turbulent quantities Up: Computation set-up Next: Physical model set-up

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