Porous Media modeling
 

How do i define a region to be porous?

I was working with the tutorial part 8, 'modelling flow through a porous media'. The only thing i did not understand is whether the region has to be defined as being porous while it is modelled in Gambit, or do i just create a meshed volume and define it as porous when i import it to Fluent.

I can only proceed once i know how to create the porous media.

thanks for the help

I built the region as fluid in gambit and then define it as porous in the boundary conditions!

when you say you defined it as porous boundary condition, do you mean using the porous jump as the boundary conditio?

hi
If you want to model flow in a porous medium in fluent, you should specify the zone as fluid zone in gambit, and then in "cell zone conditions" dialog box, enable porous zone check box , and specify related parameters such as porosity.
good luck

As i know the parameter in porous zone is inertial and viscous resistance.
How to define it?
Is there any formula or something?

Would you like give an example.

Thank you. Danke.

My porous media is a cell zone :confused:

I did't use porous-jump, may be any formulation or something ?

Yes but for the porous zone (cells) has two parameters (viscous resistance and inertial resistance) that you have to specify. And you determine these two from the pressure drop vs velocity profile using the equations at the link.

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

How to calculate the diameter particle [Dp] if i use Ergun or Blake-Kozeny equation to define inertial resisitance and porosity? [see ANSYS Fluent 6.3 User's Guide - 7.19.6]

Blake-Kozeny Equation:
P/L={150*mu*(1-e)^2}/{Dp^2*e^3}*V$

where:
P/L : Pressura drop
mu : viscosity
e : void fraction
Dp : Perticle diameter
V$ : Velocity unlimited

Thank you !
Regrads
OKY

Hi This is the reply given by Mr. Jayaprakash in a previous thread discussion,

The Ergun equation assumes that the bed is filled with uniform sized and shaped particles. The sphericity parameter is used as a conversion factor for non-spherical particles (comparing the surface-volume ratio of those particles to an equivalent spherical particle).

Of course, for fully spherical particle, the sphericity = 1.

Sphericity = (6/Dp)/(Sp/Vp)

Dp = Diameter of the particle
Sp = Surface area of the particle
Vp = Volume of the particle

For 'not so crazy' shapes, like sand particles, you can use sphericity around 0.8 - 0.9.

Complete list of sphericity values can be found in "Perry's Chemical Engineers Handbook", or "Unit Operations of Chemical Engineering by McCage, Smith and Harriot" or similar books

How to calculate the heat transfer in porous media [for conduction and convection heat transfer]?

Thank you,
Regrads
OKY

Hi everyone,

I'm trying simulation porous media in rectangular channel, but the result isn't suitable with any research.

So, would you help me. I wish someone can check my simulation and give some reports if there is something wrong.

Thank you for your help.
Please send your e-mail, than i will send you my works to to your email.
my e-mail: oky.andytya.net@gmail.com

Regrads,
OKY Andytya P

note:
I use ANSYS Fluent 6.3 [CFD]

Hi friends,
I'm simulating a tube with water flow.
The tube encounters boiling near the wall.
I intend to calculate 'void fraction versus enthalpy' along the channel.
Can you help me how to calculate void fraction?

I'm in an emergency condition.
Waiting for your comments!!!

Thanks Everybody

Hi,

I want ask, how to get the value of convection coefficien [h] from Fluent directly ?

Thank you, regrads

OKY

Porous Jump
 

Hi,

I am having problems with specifying the boundary condition of a bottom wall of a 3D rectangular channel as a "porous jump" . In GAMBIT I select Boundary type as "Porous Jump" however, when I import my mesh in FLUENT I receive an error stating that: "Cannot change porous to porous-jump because
there is only one adjacent cell thread". I am not sure what that means, can anyone please help me with this case. Any suggestion is appreciated.

Thanks,
Akim

hi

had you been able to simulate your flow through porous??
if so please contact me..

zaynah

Hi Akim,

I am modelling a tube through which mixture of air and water passes and there is an air permeable membrane around the internal wall of the tube which is permeable to air only. I should model this as VOF in Fluent.

First, I need to set this wall boundary as Porous Jump in Gambit. I did the following steps in Gambit and when importing the mesh into Fluent, I got the same Error Message as you got: "Cannot change porous to porous-jump because there is only one adjacent cell thread".

1) created a cylinder as volume
2) meshed it
3) set the boundaries as inflow, outflow, and porous jump (for the volume)
4) set the fluid zone
5) export the mesh to Fluent

I was wondering if you could get rid of this Error Messsage and how?

Or if any body else can help me model this case, it is much appriciated!

Thanks,
Leram

Porous media modeling
 

What is the most suitable software to simulat a porous media(some thing like flow past a fabric) and pressure drops?
CFX or Fluent?

http://i42.tinypic.com/orowvk.png

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.

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

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.

Porous media
 

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??

Porous media
 

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