No Temperature change in iTOUGH2 forward model run, problems with atmospheric blocks

Hi Stefan,

I currently have a couple of issues when running iTOUGH2 in forward mode, especially when trying to add topography (done using PyTOUGH).

  1. Often my outputs will simulate fluid flow and pressure changes, yet there will be no change in temperature distribution from start to finish of the model run.
     
  2. In a successful model run, topography was modelled by varying the thickness of the top layer cells. However - this means that these surface cells can sometimes have thicknesses far greater than the standard cell size. To correct this I increased the total thickness of my model and lowered the topography coordinates (such that the ground surface ‘cuts’ into the top of the model). See included pictures.

    This change caused the model to simulate no change in temperature as described in point 1). (Other than changing the RE1 parameter from 1e-8 in the successful to 1e-5 in the unsuccessful, no other changes were made).



  3. This temperature issue also arises when I try running a model using the initial conditions of a previous model run (i.e. using flow.sav). This is using the bash command itough2 –i flow.sav invfile flow.inp 7
     
  4. As far as I am aware, topography is simulated by making cells above the ground surface in the low elevation regions inactive. Do the ground surface active cells in these low topography regions take the hydrostatic effect of the above inactive cells into account?
     
  5. At the end of a model run the top cells have pressures 30x greater than that of atmospheric pressure - how would this arise if they are connected to the atmospheric blocks (atmospheric pressure at infinite volume)?

Do you know why a lack of change in temperature would occur?

I have included the flow.inp/incon/invfile files for the successful and unsuccessful runs if they can be of any use to understanding the problem. The bash command I use is itough2 –i incon invfile flow.inp 7 &

Thanks,

Hamish

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  • Hamish,

    Just a few quick questions and comments:

    (1) Which EOS are you using (infile says EOS7, primary variables appear to be for EOS3)?

    (2) I find RE1=1e-9 in unsuccessful.inp, not 1e-5 as stated in your post.

    (3) Your temperature in unsuccessful_incon are above the critical point of water - don't expect this to give accurate results (I'm surprised it runs at all).

    (4) How long out did you run this? I.e., at what point in time did you see "no temperature changes and overpressures"?

    (5) The times in block TIMES are too closely spaced, i.e., you may not get a temperature increase if you set RE1=1e-5, because  convergence always happens in ITER=1 and primary variables are not updated. Set MOP(1)=1 to check.

    (6) I propose to set MOP(16)=4 and reduce MCYC to keep the output file manageable. Here is the PARAM block I used:

    PARAM----1--MOP:123456789012345678901234----*----5----*----6----*----7----*----8
     8 2 100      10100000900001000400000000
     0.000e+00           1.000e+02 0.000e+00          9.8100e+004.0000e+001.0000e+00
    1.0000e-051.0000e+00          1.0000e+001.0000e+00

    (7) Most importantly: I cannot reproduce your erratic results, also for your unsuccessful files (the only change I made is changing the PARAM block as shown under Point (6)), i.e., I get temperature changes and no overpressures near the surface.

    (8) Disclaimer: I obviously only spent a few minutes on this, so I do not understand the model you set up or have analyzed the output in detail; still, I hope the few comments above are useful.

    Stefan

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  • Hi Stefan,

    Upon closer inspection I think most of the problems are to do with temperatures reaching above the critical point of water. Decreasing the thermal gradient of the incon file allows it run without problems.

    Thanks,

    Hamish

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