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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 , TKE dissipation rate $\epsilon$ and kinematic eddy viscosity $\nu_t$ must be specified.

Configuration file for turbulent kinematic energy

:
# 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: (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 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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Next: Center of mass of Up: Notes on gravitational potential Previous: Potential of a homogeneous Contents Index

Hydrostatic pressure

Let us consider an incompressible fluid at rest in the presence of a homogeneous gravitational field so it is supported by walls of some, possibly open, vessel. Inside a volume of the fluid there is the well known hydrostatic pressure, let us denote it by $\color{white} p$ . Assume the fluid has one free^3.5 part of its boundary, i.e. one part of its surface forms a level, i.e. plane or its part. Let us denote by

a position vector^3.6 of an arbitrary point of this plane. Hence for $\color{white} p$ holds

Notice the relation (

) is valid inside the volume of the fluid only. If we need to extend its domain, it is necessary to assure zero values for $\color{white} p$ outside of the volume of the fluid. For instance, this is satisfied naturally, if we consider $\color{white} \varrho$ a constant scalar field but vanishing outside the volume of the fluid.

Next: Center of mass of Up: Notes on gravitational potential Previous: Potential of a homogeneous Contents Index

Previous: TCFD Solvers Up: TCFD Solvers Next: blueDyMSolver – transient, incompressible
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BlueSolver - steady state, incompressible

TCFD solver for steady state, incompressible fluid flow is called blueSolver. It was gradually developed during the time from the simpleFoam solver. In any matters the blueSolver behaves the same way as any standard OpenFOAM solver. It is compatible with all OpenFOAM applications and libraries. Solver is modified to be more robust, it can use MRF method, limits for variables can be specified and many other changes have been done.

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