CFD Online Discussion Forums - vaporize water

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vaporize water - boundary conditions

Hi together,

i am working on a testcase in which water vaporizes on a heated wire (diameter = 0,1 mm)

The case is working well but i 've problems with my BC couse my steam don't get out of my integration area. In the video i added you can see that its circulating in the case but i wanna let it out.

VIDEO : http://ww3.cad.de/foren/ubb/uploads/...eWater.mpg.zip

So my Boundary-File looks like that:

Code:



top

{

    type            patch;

    nFaces          100;

    startFace       42335;

}bottom

{

    type            patch;

    nFaces          100;

    startFace       42435;

}

right

{

    type            slip;

    nFaces          170;

    startFace       42535;

}

symmetryZY

{

    type            symmetryPlane;

    nFaces          300;

    startFace       42705;

}

heat

{

    type            wall;

    nFaces          60;

    startFace       43005;

}

empty

{

    type            empty;

    nFaces          42700;

    startFace       43065;

}

my U and p_rgh files are:

Code:

dimensions      [ 0 1 -1 0 0 ];internalField   uniform ( 0 0 0 );

boundaryField

{

    symmetryZY

    {

        type            symmetryPlane;

    }

    heat

    {

        type            fixedValue;

        value           uniform ( 0 0 0 );

    }

    empty

    {

        type            empty;

    }

    right

    {

        type            slip;

    }

    bottom

    {

        type            outletInlet;

        value           $internalField;

        outletValue     $internalField;

    }

    top

    {

        type            inletOutlet;

        inletValue      $internalField;

        value           $internalField;

    }

}

and the p_rgh file is:

Code:

dimensions      [ 1 -1 -2 0 0 ];internalField   uniform 101325;

boundaryField

{

    symmetryZY

    {

        type            symmetryPlane;

    }

    heat

    {

        type            buoyantPressure;

        value           $internalField;

    }

    empty

    {

        type            empty;

    }

    right

    {

        type            slip;

    }

    top

    {

        type            totalPressure;

        phi             phi;

        U               U;

        gamma           1;

        rho             rho;

        psi             none;

        p0              $internalField;

        value           $internalField;

    }

    bottom

    {

        type            buoyantPressure;

        value           $internalField;

    }

}

Any tricks or suggestions?
Thx in advance,
Tobi

hi
first of All, what is your solver?
second i may try inletOutlet or zeroGradient for bottom in U

Quote:

Originally Posted by nimasam (Post 333674)

hi
first of All, what is your solver?
second i may try inletOutlet or zeroGradient for bottom in U

Hey nimasam,

my Solver is interPhaseChangeFoam with implement temperatur field and temperatur depended pSat.

Okay i ll try inletOutlet/zeroGradient for the bottom.
I 've tryed to use pressureInletOutletVelocity for the top BC like in the tutorial "breakdam" but the steam can not get out.

okay i ll change the bottom BC and ll tell you if its working.

Thx for replaying
Tobi

Hi,

i 've solved the case with your advice to change the bottom to zeroGradient or inletOutlet (refer to U).

The steam doesn#t get out of the boundarys :(

Hi Tobi,

Do you have a reference for the temperature dependent Psat model that you are using?

Thanks, Eric

Quote:

Originally Posted by egp (Post 334530)

Hi Tobi,

Do you have a reference for the temperature dependent Psat model that you are using?

Thanks, Eric

Hi Eric, yes i have the temperature dependent Psat correlation from August-Roche-Magnus.

My simulation is working now and the solution seeems very good.
But i am waiting for experimental values.

I am still trying to get a good solution and handle the BC for that case.
Hope i could help you.

Tobi

Hi Tobi,

Thanks. Can you give me a citation for August-Roche-Magnus?

There is a student in our group who is looking at laser-induced vaporization for creating a bubble. Very high-temperature, short duration pulse of energy. She has the heat-transfer and energy absorption modeled, and is now working on the vaporization.

Eric

Quote:

Originally Posted by Tobi (Post 334539)

Quote:

Originally Posted by egp (Post 334540)

Hi Eric,

i used the equation from http://www.tfd.chalmers.se
I ve no citation for that - exept google and wiki :)

and you can implement it with that code:

Code:

{

const dimensionedScalar t30_11("30.11", dimensionSet(0,0,0,1,0,0,0), 30.11);

const dimensionedScalar t273_15("273.15", dimensionSet(0,0,0,1,0,0,0), 273.15);

const dimensionedScalar t1("1", dimensionSet(0,0,0,1,0,0,0), 1);

const dimensionedScalar p610_94("610.94", dimensionSet(1,-1,-2,0,0,0,0), 610.94);

// dimensionSet( [kg], [m], [s], [K], [kg*mol], [A], [cd]), [kg/(m*S^2)]=[Pa]

// August-Roche-Magnus formula

pSat = p610_94 * exp( 17.625*(T-t273_15) / max(t1, T-t30_11) );

//max(1,...) is included to avoid problems with devision by 0

}

Tobi

PS: I am interested to get the bubbles involved in my solver couse i wanna simulate the heat transfer from a heated wire.

Like -
free convection
bubble convection
and film convection

i am not sure if thats correct translated but in my case i don 't get bubbles.