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-   -   Porosity changes (http://www.cfd-online.com/Forums/openfoam/109423-porosity-changes.html)

vahidzanganeh November 17, 2012 04:15

Porosity changes
 
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

nimasam November 17, 2012 15:14

dear vahid
specify your problem with much more clarification and insert one simple test case

vahidzanganeh November 19, 2012 12:01

Quote:

Originally Posted by nimasam (Post 392710)
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 !!!!

nimasam November 19, 2012 12:53

which version of OpenFOAM, do you use?

vahidzanganeh November 19, 2012 16:05

openfoam2.1.1
can you help me?

nimasam November 20, 2012 12:11

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?

vahidzanganeh November 20, 2012 12:51

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;
}
}

)

nimasam November 20, 2012 13:51

dear vahid
you are right, it seems it is a bug, so report it as a bug

vahidzanganeh November 21, 2012 02:30

hello nimasam
i dont know!!!
i have to work on combustion in porous mdeia.
I have hard problems in modeling!!

nimasam November 21, 2012 16:11

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

vahidzanganeh November 23, 2012 04:42

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.
vahid

nimasam November 23, 2012 15:58

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 ;)

vahidzanganeh November 23, 2012 17:13

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.
vahid

nimasam November 24, 2012 15:56

here, you can find contact info:
http://www.cfd-online.com/Forums/members/nimasam.html

hesamgh April 20, 2013 05:04

porous value
 
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 (Post 393239)
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;
}
}

)


vahidzanganeh April 22, 2013 02:43

Dear hesam
I think is betterd enter the amount of porosity in the Darcy-Forchheimer coefficient.
what are alpha, beta,a,b?

hesamgh April 23, 2013 02:50

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 (Post 422219)
Dear hesam
I think is betterd enter the amount of porosity in the Darcy-Forchheimer coefficient.
what are alpha, beta,a,b?


vahidzanganeh April 24, 2013 04:05

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

hesamgh April 28, 2013 04:25

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 (Post 422749)
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


vahidzanganeh April 28, 2013 05:50

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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