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rupakbanerjee August 28, 2010 15:56

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

s25011 August 31, 2010 17:15

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

Quote:

Originally Posted by rupakbanerjee (Post 273200)
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


rupakbanerjee August 31, 2010 17:34

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

Mansureh September 4, 2010 04:39

Quote:

Originally Posted by rupakbanerjee (Post 273533)
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

oky November 18, 2010 02:16

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.

snow November 18, 2010 15:30

http://www.cfd-online.com/Wiki/Fluen...e_drop_data.3F

oky November 22, 2010 22:49

Quote:

Originally Posted by snow (Post 283961)

My porous media is a cell zone :confused:

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

snow November 23, 2010 06:11

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.

nelly December 2, 2010 06:17

Quote:

Originally Posted by oky (Post 283858)
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.

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

oky December 20, 2010 03:01

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

nelly December 20, 2010 04:25

Quote:

Originally Posted by oky (Post 287822)
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

oky December 21, 2010 20:56

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

Thank you,
Regrads
OKY

oky February 1, 2011 20:53

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]

motahar May 20, 2011 03:42

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

oky May 24, 2011 23:04

Hi,

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

Thank you, regrads

OKY

Akim679 March 18, 2012 14:11

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

zaynah04 September 8, 2012 15:53

hi

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

zaynah

Leram March 6, 2013 09:01

Quote:

Originally Posted by Akim679 (Post 350090)
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 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

hadi.iraji May 15, 2013 10:36

http://aerojet.engr.ucdavis.edu/fluenthelp/tutfiles/

chocolater August 21, 2013 16:17

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

will321321 April 24, 2014 03:00

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:

jeeeban1985 August 19, 2014 01:32

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.

osamaraad October 5, 2014 15:16

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

mrh111 July 20, 2015 14:48

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

bmayurm July 21, 2015 06:29

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

vasudev1997 December 28, 2017 07:50

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

chocolater December 28, 2017 14:22

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.

vasudev1997 December 28, 2017 20:11

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.

ENGRTAHIR January 4, 2018 03:00

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.

koltesomesh20 October 4, 2019 13:32

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??

koltesomesh20 October 4, 2019 13:35

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


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