Heating a soil matrix that contains water

Numerical methods and mathematical models of Elmer
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MrChips
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Heating a soil matrix that contains water

Post by MrChips »

I have been reading all the forum threads I can find on phase change. Mzenkers threads (viewtopic.php?f=3&t=852 and viewtopic.php?f=3&t=2345&start=20) have been particularly helpful.

Maybe my case is too complex. Essentially, I want to model the expansion of water and steam in a porous media such as soil. Saturated soil is heated via an internal source. The water and soil heat up, a phase change occurs, and steam is generated and expands through the soil. I understand that I need to define enthalpy over the temperature characteristic of the material. I suspect the thermal conductivity will change with the phase change and I will need to account for that as well. However, I am having trouble with the concept that my model body will essentially be two materials instead of one. One material is stationary while the other is free to move around.

Just conceptually, can anybody give me a nudge in the right direction?
MrChips
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Re: Heating a soil matrix that contains water

Post by MrChips »

I guess there's not a straight forward way to do this currently. I thought maybe specifying the bulk properties of the soil/water (bulk thermal conductivity, bulk heat capacity, bulk density, etc) would allow me to get some distance with this, and maybe it does from a heat conduction perspective. However, after some thought, without being able to specify multiple material properties within the same body it is just not going to work from a fluid flow perspective.

I need to learn some fortran...
raback
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Re: Heating a soil matrix that contains water

Post by raback »

Hi

Yes, multiphase modeling tends to be complicated. If you can write down the equations you need to solve I can give you some hints. The devil often lies in the detail of the formulation. Luckily in your case the Reynolds number will probably be small so you don't need to mix in turbulence.

I guess a crucial question is whether you need different velocities for each phase or if you can deal the problem with mean velocity and volume fraction of the different species (where soil has velocity zero).

-Peter
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