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effect of porosity in the porous media

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Old   October 13, 2014, 10:02
Default effect of porosity in the porous media
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Hello to all,

I am modeling two-phase flow (water and air) through a channel that as a porous and a non-porous region.

I am confused about the effects of the porosity of the porous media in the simulation. By reading Fluent's manual I understand that, as I was expecting, porosity is the void space of the porous region, i.e., the space where the fluid(s) can flow.

However, when i changed the porosity, the results are not as i expected. In the figure attached*, you can observed that increasing the porosity makes water to flow "slower" in the porous media, and i was expecting the opposite!

* Air is entering at the upper part of the channel (from left to right) while water is entering at the bottom part of the channel (the porous media) and through a porous directly into the upper part of the channel

I also found in Fluent's manual that porosity affects heat transfer properties (which is not considered here) and the time-derivative in the continuity equation. However, I don't understand how can this lead to the results i obtained.

Can someone help me? Thanks!
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Old   October 22, 2014, 13:03
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The answer to this question:

"With a low porosity the physical velocity is higher and therefore the water would seem to flow faster. Essentially at low porosity there is less open volume and therefore for a given inlet volumetric flow the time to fill will reduce. At a porosity of 1 the volume is at its maximum and therefore the time to fill is longest."

Thanks to David Stanbridge (swiftaircraft)
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