[nadine]

Hello All,

I am adding the enrgy equation to porousinterfoam using the enthalpy formulation. So for my conductivity calculation, i need to multiply each material conductivity with the cell porosity.

I search around to find out how to use the cell porosity but I didn't have any luck, so please can anyone lead me with his or her suggestions?

Thank you all,
Nadine

[Natalie2210]

Hi!

I'm afraid I cannot help you with your original question but I wonder whether you tried some simple cases with porousInterFoam?

for example, if a so-called "rectilinear flow" is considered which is basically a 1D flow (imagine a rectangle where you have the inlet on the left hand side and the outlet on the right) there is an analytical solution to the flow front progression,

xf = sqrt(2*K*P0*t/(mu*eps))

where xf denotes the flow front progression, K the permeability of the porous medium, P0 the injection pressure, mu the viscosity in Pa*s and eps the porosity.

Now, as far as I have gleaned, the porosity eps is not taken into account when using the porousInterFoam solver but even if I assume eps=1, the solver does not yield correct results. Have you /has anyone experienced this problem?

There have been some discussions last year to that topic and I also found a debugged version of the porousInterFoam solver (http://sourceforge.net/apps/mantisbt...iew.php?id=129) which should repair the problem of not taking the porosity into account. I'm trying to compile this debugged version and I will let you know whether this fixes the problem I described above, but still, I'm curious of your experiences with porousInterFoam.

Greetings, Natalie

[Cyp]

Originally Posted by Natalie2210

Hi!

I'm afraid I cannot help you with your original question but I wonder whether you tried some simple cases with porousInterFoam?

for example, if a so-called "rectilinear flow" is considered which is basically a 1D flow (imagine a rectangle where you have the inlet on the left hand side and the outlet on the right) there is an analytical solution to the flow front progression,

xf = sqrt(2*K*P0*t/(mu*eps))

where xf denotes the flow front progression, K the permeability of the porous medium, P0 the injection pressure, mu the viscosity in Pa*s and eps the porosity.

Now, as far as I have gleaned, the porosity eps is not taken into account when using the porousInterFoam solver but even if I assume eps=1, the solver does not yield correct results. Have you /has anyone experienced this problem?

There have been some discussions last year to that topic and I also found a debugged version of the porousInterFoam solver (http://sourceforge.net/apps/mantisbt...iew.php?id=129) which should repair the problem of not taking the porosity into account. I'm trying to compile this debugged version and I will let you know whether this fixes the problem I described above, but still, I'm curious of your experiences with porousInterFoam.

Greetings, Natalie

Dear Natalie and Nadine,

I would like to add some lights about porousInterFoam.

Actually, porousInterFoam does not simulate two phase flow in porous media, expect in some very special cases (as the Hele-Shaw cells). This solver is not consistent with the two-phase flow physic in porous media.

You have to keep in mind that porous media laws are in fact averaged equations. That means that in one cell of the mesh, you have both fluid and solid, even if this latter is not physically represented. In two-phase flow through porous material, we use the concept of saturation S, which is the rate of liquid over the void space volume of the cell. Basically, S varyies on the range [0,1].

The problem with porousInterFoam, is that this solver is just a VOF solver with additionnal resistance source terms. With that solver, the saturation does not exist and the phase indicator is either equal to 0 or 1. You can't have value in between (for exemple, S=0.4 means that the void space of a cell is filled by 40% liquid and 60% gas). So, in my opinion, this solver has absolutely no meanings.

I think the right solution is to program a solver based on IMPES method (see a presentation I made at OFW7 for additionnal details).

Best regards,
Cyp

[ngj]

Hi Cyp,

Please allow me to disagree, since I exactly know the debugged version that Natalie referred to, as I myself posted that particular report. The debugged version corrects for the previous error that computational cells with a solid present did not fill faster than cells without a solid.

The solution to this error was straight forward, because MULES was actually prepared to this type of flows, though the interface was not utilised in porousInterFoam.

We had a master student, who tested the solver and he obtained good results in comparison with experimental data for coastal engineering size problems (dimensions of many meters in each direction).

Kind regards,

Niels

P.S. There has not been a response to the bug report, since the error is still present in version 2.2.0.

[Cyp]

Originally Posted by ngj

Hi Cyp,

Please allow me to disagree, since I exactly know the debugged version that Natalie referred to, as I myself posted that particular report. The debugged version corrects for the previous error that computational cells with a solid present did not fill faster than cells without a solid.

The solution to this error was straight forward, because MULES was actually prepared to this type of flows, though the interface was not utilised in porousInterFoam.

We had a master student, who tested the solver and he obtained good results in comparison with experimental data for coastal engineering size problems (dimensions of many meters in each direction).

Kind regards,

Niels

P.S. There has not been a response to the bug report, since the error is still present in version 2.2.0.

Yes, but with porousInterFoam, even with the debugged version, you can't have gas AND liquid in the same cell, can you ?

[ngj]

Hi Cyp,

I have just gone through your presentation, and I now understand what you mean. For your problems, where the saturation is of importance, then porousInterFoam will not work, because the two fluids are considered as immiscible.

For coastal engineering problems, however, where there is a pretty clear interface between air and water, capillary effects can largely be neglected in man made structure and grain sizes are say 10 cm or larger, porousInterFoam does a pretty good job.

I have tried reading the posts by Nadine and Natalie, however, it is a bit unclear to me, which effects are of importance to them.

All the best,

Niels