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Old   November 17, 2012, 04:15
Default Porosity changes
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Hello Foamers.
I want to model a flow with a porous zone which works well using rhoPorousSimpleFoam in OF 2.1.x.
I want to examine the effect of porosity on the answers. But change does not change the porosity of the porousZones.H in the constant folder. I think it is not used at all porosities.
Who can help me?
Best regards.
vahid
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Old   November 17, 2012, 15:14
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dear vahid
specify your problem with much more clarification and insert one simple test case
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Old   November 19, 2012, 12:01
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Quote:
Originally Posted by nimasam View Post
dear vahid
specify your problem with much more clarification and insert one simple test case
dear nimasam


I am working a new solver for combustion in porous media. i work on two solver reactingFoam and rhoPorousReactnhFoam for simolation combustion in porous media.
i think the solver rhoPorousMRFSimpleFoam only the initial porosity(porosity=1) and dont used amount of porosity(for example porosity=0.781 define in porousZones.H in the constant folder).
i thenk the porosity is private on class porousZone and the solver dont used the amount of porosity. the solver used amount of default in porousZones.C !!!!
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Old   November 19, 2012, 12:53
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which version of OpenFOAM, do you use?
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Old   November 19, 2012, 16:05
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openfoam2.1.1
can you help me?

Last edited by vahidzanganeh; November 19, 2012 at 16:27.
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Old   November 20, 2012, 12:11
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Code:
1
(
    porosity
    {
        coordinateSystem
        {
            e1  (0.70710678 0.70710678 0);
            e2  (0 0 1);
        }

        Darcy
        {
            d   d [0 -2 0 0 0 0 0] (5e7 -1000 -1000);
            f   f [0 -1 0 0 0 0 0] (0 0 0);
        }

        thermalModel
        {
            type        none; // fixedTemperature;

            // fixedTemperature coefficients
            T           350;
        }
    }
)
tell me what is e1 and e2 ? and whats you argument about?
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Old   November 20, 2012, 12:51
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hellow nimasam
my model is
1
(
porosity
{
coordinateSystem
{
e1 (0.70710678 0.70710678 0);
e2 (0 0 1);
}
porosity 0.8;

Darcy
{
d d [0 -2 0 0 0 0 0] (5e7 -1000 -1000);
f f [0 -1 0 0 0 0 0] (0 0 0);
}

thermalModel
{
type none; //fixedTemperature;

// fixedTemperature coefficients
T 350;//1350;
}
}

)
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Old   November 20, 2012, 13:51
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dear vahid
you are right, it seems it is a bug, so report it as a bug
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Old   November 21, 2012, 02:30
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hello nimasam
i dont know!!!
i have to work on combustion in porous mdeia.
I have hard problems in modeling!!
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Old   November 21, 2012, 16:11
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maybe you want to look in source code, where it uses porosity,
However combustion is a complex phenomena, you need to be expert in existing solvers then try to implement new code, so
1-try to understand existing test case,
2-find nearer solvers to your case
3-read source codes, find out what each part does
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Old   November 23, 2012, 04:42
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hello nimasam
I have searched the reference code. porous media is modeled attenuting the time derivative and by adding sink term to the navier stokes eqn. sorce term is viscous and inertial lose.
but my momentum eqn should be porosity multiplied the other terms in porous zone in adding to the above.
How do you know that?

Best regards.
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Old   November 23, 2012, 15:58
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you should learn how to program in OpenFOAM, maybe reading user guide and programmer guide and reading source codes, help you to get familiar with coding at OpenFOAM, if you want more, you can connect me
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Old   November 23, 2012, 17:13
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hello nimasam
I'm willing to be in contact with you more. thanx alot give me email adress :-)
of course i have read user guide ago.
Best regards.
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Old   November 24, 2012, 15:56
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here, you can find contact info:
http://www.cfd-online.com/Forums/members/nimasam.html
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Old   April 20, 2013, 05:04
Default porous value
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hellow
dear vahid
how can i chenge my porous value in openfoam 2.0.1?
can you explain me how do you got that value of alpha,beta ,a,b?

thanks alot
Quote:
Originally Posted by vahidzanganeh View Post
hellow nimasam
my model is
1
(
porosity
{
coordinateSystem
{
e1 (0.70710678 0.70710678 0);
e2 (0 0 1);
}
porosity 0.8;

Darcy
{
d d [0 -2 0 0 0 0 0] (5e7 -1000 -1000);
f f [0 -1 0 0 0 0 0] (0 0 0);
}

thermalModel
{
type none; //fixedTemperature;

// fixedTemperature coefficients
T 350;//1350;
}
}

)
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Old   April 22, 2013, 02:43
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Dear hesam
I think is betterd enter the amount of porosity in the Darcy-Forchheimer coefficient.
what are alpha, beta,a,b?
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Old   April 23, 2013, 02:50
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would you explain me what are the darcy's coefficient?
i saw some where there are alpha,beta,a,b that calculate the porosity when the material isn't isotoropic !!!

thank you



Quote:
Originally Posted by vahidzanganeh View Post
Dear hesam
I think is betterd enter the amount of porosity in the Darcy-Forchheimer coefficient.
what are alpha, beta,a,b?
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Old   April 24, 2013, 04:05
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dear hesam
you can check files in "/opt/openfoam211/src/finiteVolume/cfdTools/general/porousMedia"
or do research on the references about the porous medium equation.
best regards
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Old   April 28, 2013, 04:25
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dear vahid i checked the location that you mentioned...

these are the coefficient that i said:


a = 9.367
b = 1.029E7
alphax = 0.5 * a * density [kg/m^4]
betax = viscocity * b [kg/m^3s]

d= beta/viscocity [1/m^2]
f=2*alpha/density [1/m]

alphay=1e6
betay=1e6

alphaz=1e6
betaz=1e6

viscocity=1.663e-5 kg/ms
density=0.61935 at Inlet

coordinateSystem
{

e1 (1 0 0);
e2 (0 0 1);
}

Darcy
{
d d [0 -2 0 0 0 0 0] (1.029e7 (6.01e10??) (6.01e10??));
f f [0 -1 0 0 0 0 0] (18.367 (?) (?));

these are for ceramics, i want to know from where i can obtain them??

thanks alot for your help vahid



Quote:
Originally Posted by vahidzanganeh View Post
dear hesam
you can check files in "/opt/openfoam211/src/finiteVolume/cfdTools/general/porousMedia"
or do research on the references about the porous medium equation.
best regards
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Old   April 28, 2013, 05:50
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dear hesam
d and f are Darcy-Forchheimer coefficient and has been explained in ...cfdTools/general/porousMedia/porousZone.H, or you can read "porous media in openfoam.pdf" in internet.
but if you have new equations you can define them. you can do this with reading user guide, programmer guide and reading source codes.
best regards
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