[Nico A.]

Dear FOAMers,

I am simulating a (laminar) natural convection boundary layer in 2D with the above-named solver. So my domain has a uniformly heated wall at the left and atmospheric inlet and outlet conditions at the top, bottom and right respectivly. The domain is attached.

The case is already running with the following BCs for T, U, p_rgh:

0/T

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

dimensions      [ 0 0 0 1 0 0 0 ];

internalField   uniform 288.15;

boundaryField
{
    heatedWall
    {
        type            fixedValue;
        value           uniform 298.15;
    }
    right
    {
        type            inletOutlet;
        inletValue      uniform 288.15;
        value           uniform 288.15;
    }
   
    frontAndBack
    {
        type            empty;
    }
    inlet
    {
        type            inletOutlet;
        inletValue      uniform 288.15;
        value           uniform 288.15;
    }
    outlet
    {
        type            zeroGradient;
    }
}


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

0/U

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

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

internalField   uniform ( 0 0 0 );

boundaryField
{
    heatedWall
    {
        type            fixedValue;
        value           uniform ( 0 0 0 );
    }
    
    right
    {
        type            pressureDirectedInletVelocity;
    value        uniform (0 0 0);
    inletDirection  uniform (-1 0 0);
    }
    
    frontAndBack
    {
        type            empty;
    }
    
    inlet
    {
        type            pressureInletOutletVelocity;
    value        uniform (0 0 0);
    }
    
    outlet
    {
        type            inletOutlet;
        inletValue      uniform ( 0 0 0 );
        value           uniform ( 0 0 0 );        
    }
}

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

0/p_rgh

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

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

internalField   uniform 0;

boundaryField
{
    heatedWall
    {
        type            buoyantPressure;
    rho        rhok;
        value           uniform 0;
    }
    
    right
    {
        type            totalPressure;
        U               U;
        phi             phi;
        rho             rhok;
        psi             none;
        gamma           1.4;
        p0              uniform 0;
    }
    
    frontAndBack
    {
        type            empty;
    }
    
    inlet
    {
        type            totalPressure;
        U               U;
        phi             phi;
        rho             rhok;
        psi             none;
        gamma           1.4;
        p0              uniform 0; 
    }
     
    outlet
    {
    type            buoyantPressure;
    rho        rhok;
        value           uniform 0;   
    }
}

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

For the temperature difference of 10K and other flow parameters, the Rayleigh number is Ra=10^6, so a laminar boundary layer will develop, as you can see in the attached pictures for the Uz and T distribution at the vertical wall. The results seem to be physically correct.

But when I look at the residuals, they are oscillating (see attached picture). Normally they should fall due to given tolerances/ convergence criterions of 10^-08. The results are nearly the same for upwind and linear div-schemes.

I appreciate any suggestion regarding this case.

Best regards,
Nico

[vnarayana]

Dear Nico,
Good evening i am doing natural convection using buoyantBoussinesqSimplefoam , please tell me how to plot residuals(convergence history). for a particular point (x,y), how to find maximum velocity. i used pyFoamPlotWatcher.py it is not working ? how to use foamLog in buoyantBoussinesqSimpleFoam ?
Thank you

[karlli]

Dear Nico,
Please post your fvSolution file, could it be that your solver tolerance is set at 1e-4 where you experience the noise?

Best Regards,
Karl