Neumann BC

Dear Users,

I have been solving an HT model using OGS. I am using Neuman BC defined in the Sourceterm file (ST). Acording to the turorial Watanabi et al. (2012) neuman BC are defined in ST. However the OGS is giving me an error when I dot this because doundary conditions for LIWUID_FLOW are missing. What is this? I suppposed that once the source terms are defined we don’t need to specify anything in the file BC. This is confusing. Can somebody tell me how to solve this? Thanks in advance.

Jhonny

You can ignore the warning message if it's your intention. OGS should be able to run simulations with only STs although you need to carefully check results.

Best,
nori

···

On 07/23/2016 12:07 PM, Jhonny Encalada wrote:

Dear Users,

I have been solving an HT model using OGS. I am using Neuman BC defined
in the Sourceterm file (ST). Acording to the turorial Watanabi et al.
(2012) neuman BC are defined in ST. However the OGS is giving me an
error when I dot this because doundary conditions for LIWUID_FLOW are
missing. What is this? I suppposed that once the source terms are
defined we don't need to specify anything in the file BC. This is
confusing. Can somebody tell me how to solve this? Thanks in advance.

Jhonny

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Dear Nori,

I have tried to run under this conditions; however a Liquid Flow process does not converge after 3000 linear iterations. But When I use at least one BC and source terms the solution converges and gives results. Btw, I was also wondering why the nodal velocity in the injection and extraction points always is wrong. It changes from the highest to the lowest value in the elements just around the mentioned points and he velocity in these points is almost zero?. I have adjusted the tolerances but it does not work. It does not matter the dimension of my mesh also.

Thanks for the reply!

···

On Monday, 25 July 2016 06:13:38 UTC+1, Norihiro Watanabe wrote:

You can ignore the warning message if it’s your intention. OGS should be able to run simulations with only STs although you need to carefully check results.

Best,
nori

On 07/23/2016 12:07 PM, Jhonny Encalada wrote:

Dear Users,

I have been solving an HT model using OGS. I am using Neuman BC defined
in the Sourceterm file (ST). Acording to the turorial Watanabi et al.
(2012) neuman BC are defined in ST. However the OGS is giving me an
error when I dot this because doundary conditions for LIWUID_FLOW are
missing. What is this? I suppposed that once the source terms are
defined we don’t need to specify anything in the file BC. This is
confusing. Can somebody tell me how to solve this? Thanks in advance.

Jhonny


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Hi,

I guess you tried to simulate steady-state of the liquid flow process. In that case, if you don't specify Dirichlet BCs, there is no unique solution in terms of absolute pore pressure, and a linear solver may not converge. Transient simulations often work only with Neumann BCs, though you still need to check if results physically make sense or not.

OGS calculates the nodal velocity at any points by interpolation of surrounding elemental velocity. However current implementation cannot get right results if it's an injection/extraction point or it's on fracture elements. I always recommend to check element velocity instead. ParaView is quite helpful for it.

Best,
Nori

···

On 07/25/2016 05:17 PM, Jhonny Encalada wrote:

Dear Nori,

I have tried to run under this conditions; however a Liquid Flow process
does not converge after 3000 linear iterations. But When I use at least
one BC and source terms the solution converges and gives results. Btw, I
was also wondering why the nodal velocity in the injection and
extraction points always is wrong. It changes from the highest to the
lowest value in the elements just around the mentioned points and he
velocity in these points is almost zero?. I have adjusted the tolerances
but it does not work. It does not matter the dimension of my mesh also.

Thanks for the reply!

On Monday, 25 July 2016 06:13:38 UTC+1, Norihiro Watanabe wrote:

    You can ignore the warning message if it's your intention. OGS
    should be able to run simulations with only STs although you need to
    carefully check results.

    Best,
    nori

    On 07/23/2016 12:07 PM, Jhonny Encalada wrote:
    > Dear Users,
    >
    > I have been solving an HT model using OGS. I am using Neuman BC
    defined
    > in the Sourceterm file (ST). Acording to the turorial Watanabi et
    al.
    > (2012) neuman BC are defined in ST. However the OGS is giving me an
    > error when I dot this because doundary conditions for LIWUID_FLOW are
    > missing. What is this? I suppposed that once the source terms are
    > defined we don't need to specify anything in the file BC. This is
    > confusing. Can somebody tell me how to solve this? Thanks in
    advance.
    >
    > Jhonny
    >
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    > an email to ogs-users+...@googlegroups.com <javascript:>
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Norihiro Watanabe, Dr.-Ing.

Department of Environmental Informatics
Helmholtz Centre for Environmental Research - UFZ
Permoserstrasse 15, 04318 Leipzig, Germany

Tel: +49 341 235 1806
Email: norihiro.watanabe@ufz.de