# media

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 May 24, 2005, 10:29 media #1 stu Guest   Posts: n/a What is the meaning of :- porous media???

 May 24, 2005, 12:08 Re: media #2 Steve Guest   Posts: n/a Think of a sponge

 May 25, 2005, 03:10 Re: media #3 stu Guest   Posts: n/a what is sponge ??? am not an english native speaker-SORRY!

 May 25, 2005, 03:20 Re: media #4 Harry Fulmer Guest   Posts: n/a

 May 25, 2005, 04:13 Re: media #5 Steve Guest   Posts: n/a A porous medium is something that allows fluid to flow through it. Media is the plural of medium.

 May 25, 2005, 05:34 Re: media #6 stu Guest   Posts: n/a Perfect, do you think gas-liquid is a porous media, what about three-phase such as gas-liquid-oil then!!!!

 May 25, 2005, 05:48 Re: media #7 Harry Fulmer Guest   Posts: n/a no, porous media is usually a solid that allows fluid (gas or liquid) to pass 'through' or 'between' it.

 May 25, 2005, 09:21 Re: media #8 Jim_Park Guest   Posts: n/a Think of water (or oil) seeping through a bed of sand. Or air flowing through a filter.

 May 25, 2005, 11:05 Re: media #9 stu Guest   Posts: n/a This is what I want Jim, thank you. The question now is: how can one develop a mathematical model? Can we think of the two-phase flow model, two-fluid model, which suffer from too many mathematical problems as we know???? Or what about considering the relative velocity between the two phases to consider a mixture model, forget about the ill-posedness for the meantime. Any ideas then!!!!!!

 May 25, 2005, 13:17 Re: media #10 Jim_Park Guest   Posts: n/a Depends on the details of course. Often with the flow of a fluid in sand (small pores), you can model the flow using Darcy's law, which is essentially velocity = - (k/rho) grad p. (1) k is the permeability, which in the stuff I worked with was determined experimentally. Rho is the fluid density of course, and p is the pressure. This essentially replaces the momentum equations. For incompressible, take the divergence of eq. (1) and you have a continuity statement, div (v) = - div {(k/rho) [grap p]} = 0 (2) Looks a lot like a LaPlace equation, doesn't it? The equation gets a bit more complex if you consider compressible flows and/or unsteady flows. I haven't tried to weave this into an established CFD code - it always seemed to be easier to just code it up. The boundary conditions are usually on the normal component of velocity. So you use eq. (1) to get a pressure gradient on the boundary from those boundary conditions. For situations where the Darcy assumptions don't work, take a look at a two-phase formulation of the NS equations and set one phase velocity to zero. That might (?) work in a commercial CFD code with a two-phase capability. Good luck!

 May 27, 2005, 00:30 Re: media #11 yazid Guest   Posts: n/a could u please described that what u mean two-phase formulation of the NS equations and set one phase velocity to zero. That might (?) work in a commercial CFD code with a two-phase capability.

 May 27, 2005, 08:41 Re: media #12 Jim_Park Guest   Posts: n/a It'll be hard to write that out on this web site. You might want to look at Bird, Stewart, and Lightfoot, "Transport Phenomena", a classic chemical engineering text (been around for more than 50 years but periodically updated). Look at the chapters outlined in the right-hand column of table 1.

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