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 murthy October 26, 2001 23:06

modelling

Hi, I have a problem with porous media.The problem is that I want to model solid particles with a given dia. in a given quadrilateral cell.The zone may consist of 50 such cells.How do we actually model this for the 2-D case.Oe is it better to cosider the whole zone as an pressure drop zone. Murthy

 david October 29, 2001 08:33

Re: modelling

A) do u mean ur particles are creating the porous media or B) thru the porous media, another set of particles are passing through ? DC

 murthy October 29, 2001 19:36

Re: modelling

I mean the particles are creating the porous media. The porous media is composed of these spherical particles. Murthy

 david November 1, 2001 19:36

Re: modelling

A) I don't understand your problem now: Do you know the velocity/pressure-drop characteristics.? B) Can you calculate alpha and c2 ?

DC

 murthy November 1, 2001 20:09

Re: modelling

The domain consists of a bed of spherical particles whose voids make up for the flow(air).The packing may be thought of as rhombohedral.I am cosidering the domain in 2-D and dividing the domain(rectangular) into number of cell units.I am also considering each cell to hold one of the spheres. Regarding the second part,with aid of Darcy's equayion and Erguns equation for beds I think that we can get permeabilty(alpha)what is C2??? Thanks Murthy

 david November 2, 2001 02:18

Re: modelling

The permeability (alpha) and inertial loss coefficient in each component direction can be calulated from the equations 6.19.16 and 6.19.17 of the manuals. U have to detremine viscous resistance coefficients (1/alpha) and the inertial resistance coefficients (c2) in the direction of the flow. Based on the porosity and pore dia, you should be able to calculate these paramters. Its always good idea to solbe the sytem withough considering the porous media. and then solve again considering porous media. Gradually decrease the porosity.. .9 .8 .7 .6..and so on.

DC

 murthy November 2, 2001 12:41

Re: modelling

Now while solving for porous media, how do we actually model the domain.Iam considering heat transfer too. Should the domain(2-D) actually have the circles(spheres) modelled in each cell or is there any other way.Iam using Fluent 5.5 as the processor and Gambit to model the media. I am really new to Fluent,please let me know how to go about it. Thanks Murthy

 david November 4, 2001 00:06

Re: modelling

In Gambit u define the porous zone as a fluid (not solid) and then in fluent define that zone as a porous media.

DC

 yagub December 10, 2001 22:39

Re: modelling

hi I traying to simulate flow(just velocity profil) inside packed bed (spherical catalyst)and I used gambit 1.3 and fluent 5.5. and from the litrature we know the velocity is maximum near the wall because of voidage fraction is unity near the wall. therefore, how can I defined the variabl permabilty in radial direction inside the packed bed. I appreciate any one help me. thanks A.yagub

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