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Tobi November 25, 2011 11:36

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


nimasam November 26, 2011 23:35

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

Tobi November 27, 2011 07:01

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

Tobi November 28, 2011 06:02

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 :(

egp December 3, 2011 06:56

Hi Tobi,

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

Thanks, Eric

Tobi December 3, 2011 09:09

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

egp December 3, 2011 09:14

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)
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


Tobi December 3, 2011 09:40

Quote:

Originally Posted by egp (Post 334540)
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


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.


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