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Initial and boundary conditions for p and u​

  • Initial and boundary conditions are usually stored in directory /0.
  • Solver simpleFoam requires pressure p, velocity U and turbulence quantities initial and boundary conditions.
  • Number named directories represent time layouts of solution.

     

  • Configure file for pressure:
    # cat $FOAM_RUN /pitzDaily/0/p

     

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

internalField   uniform 0;

boundaryField
{
    inlet
    {
        type            zeroGradient;
    }

    outlet
    {
        type            fixedValue;
        value           uniform 0;
    }

    upperWall
    {
        type            zeroGradient;
    }

    lowerWall
    {
        type            zeroGradient;
    }

    frontAndBack
    {
        type            empty;
    }
}
  • Physical dimensions of pressure: $ m^{2}s^{-2}$ (kinematic pressure) is in OpenFOAM written as: [0 2 -2 0 0 0 0]
  • Initial condition: $ p_0 = 0$ (constant in whole flow domain)
  • Standard boundary conditions for incompressible fluid flow in a channel are following:
    • $ p_{\infty} = 0$ at the outlet of the domain
    • Pressure is extrapolated at the walls and at the inlet
    • At boundary frontAndBack (front side and back side) we set boundary condition empty, flow is not solved in this direction (quasi 3D – 2D simulation)

     

  • Configuration file for velocity:
    # cat $FOAM_RUN /pitzDaily/0/U

     

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

internalField   uniform (0 0 0);

boundaryField
{
    inlet
    {
        type            fixedValue;
        value           uniform (10 0 0);
    }

    outlet
    {
        type            zeroGradient;
    }

    upperWall
    {
        type            noSlip;
    }

    lowerWall
    {
        type            noSlip;
    }

    frontAndBack
    {
        type            empty;
    }
}
  • Physical dimensions of velocity: [0 1 -1 0 0 0 0] $ \rightarrow$ $ m/s$
  • Initial condition: $ U_0 = (10, 0, 0)$ (constant in whole domain)
  • Standard boundary conditions for incompressible fluid flow in a channel:
    • $ U_{\infty} = (10, 0, 0)$ at the inlet
    • Velocity is extrapolated at the outlet
    • Velocity is zero at the walls
    • At boundary frontAndBack (front side and back side) is boundary condition empty, flow is not solved in this direction (quasi 3D – 2D simulation)
  •  
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Previous: Computation set-up Up: Computation set-up Next: Turbulent quantities

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