Re: [DuMux] Questions about residual saturation

[Timo Koch]

Dear Nicolas, the residual saturation relates to the mobility of the phase (in terms of transport of the phase). But the “immobile” water can still evaporate, so in the compositional models in dumux by phase change the liquid saturation can still go to 0 when the gas phase is mobile. (Only then you would usually also have a phase presence state switch / primary variable switch in the CO2 model.) If there is water trapped in the rock with no pathway out whatsoever (not even through the gas phase), from a dumux perspective we would consider it part of the solid instead.   Best Timo On 31 Aug 2023, at 10:42, Mathis Kelm <mathis.k...@iws.uni-stuttgart.de> wrote:  Dear Nicolas, the volume variables and output should be the real saturations, only when evaluating the material laws do we use them to compute effective saturation. Depending on the problem you can have values outside the range between residual values, e.g. with fully saturated initial conditions. I was unable to reproduce your error, which version of DuMux are you using and which of the tests were you using? Testing both the master branch and release 3.7, if I change the values for in `test/porousmediumflow/co2/params.input` and run test_co2_box then the liquid saturation stays between 0.43 and 1.0. So it exceeds Sw = 1.0 - Snr but doesn't drop below Swr. If you haven't reached mesh convergence then the solution can depend on the discretization length. If I'm discretizing a linear solution the minimum value with naturally decrease with increased resolution. With refinement your solution and thus the minimum value should converge. Without further information it's difficult to say if there is some issue. Best regards, Mathis On 31/08/2023 09:17, Nicolas Pillardou wrote: Dear Dumux Community,  I'd like to ask you a quick question about residual saturation, which may seem trivial to you. In one of my simulations that considers two-phase flow (CO2 model), I set: Swr = 0.3 Snr = 0.05 When I look at the liquid saturation solution obtained, it is given between 0 <= S_w <= 1. Why the minimum value reached by this liquid saturation is 0 ? Shouldn't it be Sw = 0.3 instead with the residual liquid saturation ? Is the output saturation represented by the effective saturation instead of the real liquid saturation ?  I tested the same parameters in the co2 model provided in the Dumux tests and it appears to be the same behaviour. The saturation exceeds the residual saturation. I also noticed that this minimum saturation value is different for several mesh sizes. Does this seem consistent to you?  Thank you in advance for your answers. Best regards, Nicolas Pillardou _______________________________________________ DuMux mailing list DuMux@listserv.uni-stuttgart.de https://listserv.uni-stuttgart.de/mailman/listinfo/dumux -- ******************************************************** Mathis Kelm Universitaet Stuttgart Institut fuer Wasser- und Umweltsystemmodellierung Lehrstuhl fuer Hydromechanik und Hydrosystemmodellierung Pfaffenwaldring 61, 70569 Stuttgart Tel.: 0711/685-60146 mathis.k...@iws.uni-stuttgart.de https://www.iws.uni-stuttgart.de/lh2/ ******************************************************** _______________________________________________DuMux mailing listDuMux@listserv.uni-stuttgart.dehttps://listserv.uni-stuttgart.de/mailman/listinfo/dumux

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