CFD Online Discussion Forums - Porous Media modeling

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Quote:

Originally Posted by nelly (Post 285714)

Hi Oky, did you get to find the parameters?

If not, here is the explanation.

The formula is
Dp/L= [(viscosity/alpha)*velocity]+ [C2*1/2*density*velocity^2]
(dp/l =viscousr resistance + inertial resistance)

and

plot dp/l vs velocity in excel. The pressure drop can be obtained from cfd.

The values for velocity can be arbitrarily chosen say for ex. 0 to 20 m/s (even more if you want more points)

Plot Dp/L vs velocity based on above formula and examine the curve how it looks like. If it is a straight line then use only dp/l=viscous resistance.
If it is a quadratic equation use (dp/l =viscousr resistance + inertial resistance). Find K and C2 with these curves.

Hope this helps .

cheers
Nelly

Hi Nelly,

I did everything you specified above I only have two clarifications:confused:.

1.) I sometime get a negative k=permeability because when I plot DeltaP vs Velocity it gives me an equation with a -Bx. My question is, can I use this (-) Value of k as input? if not please give me a hint on how to remedy this problem.:D

2.) To get C2 and k you have to use L=Thickness. My question is what thickness to use?, the thickness of the screen which you got the experimental data from ,(P vs V), or the representative porous media's thickness used in the solver (I some times use thick Porous media for ease of meshing):p

Thanks.:)

-will:cool:

Details of Porous Media

Hello,
I am trying to understand and operate a porous media in which the void fraction is arranged in random order. Whenever I select the system as laminar, the flow is laminar and even when I select it to be turbulent, the flow is laminar. So, what are the factors we need to consider (it is very complicated to consider all points) to simulate the random arrangement of the void fraction? Further which parameters are normally selected and avoided while considering the porous media.

hi for all
I need to know the steps of build up a porous media by using fluent program
I need for these steps too much so I wish form any one who can present the assistance to support me please

Hi every body
I don't know how determine initial velocity for the flow in porous media.
Thank you for time and consideration.
Best regards

Hello Rupak Banerji,
In your first message you said about tutorial number 8. Which series of tutorial you are solving? can you share?

modelling porous surface

Hey friends
how do i model a porous surface in ansys fluent?
can i make a wall surface porous
need help

thanks in advance

Quote:

Originally Posted by vasudev1997 (Post 676285)

Hey friends
how do i model a porous surface in ansys fluent?
can i make a wall surface porous
need help

thanks in advance

It's simple, just set the "porous jump" to a zero thickness wall and fill the coefficients.

Quote:

Originally Posted by chocolater (Post 676314)

It's simple, just set the "porous jump" to a zero thickness wall and fill the coefficients.

Thanks a lot chocolater for your advice.

hi Nelly.
you said that pressure drop can be calculated from CFD.
I am working on combustion of heptane gas through porous medium. In this case how can i calculate the porous coefficient. Your help is really needed.

The Velocity in porous media shows the same as inlet pipe. Is their any difference in velocity in porous media and the velocity in empty pipe??

Is their velocity difference in porous media and the empty pipe. I doing simulation in ansys. Using physical velocity but i didnt se the difference in velocity