Boundary fluxes

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Boundary fluxes

Post by Admin » Thu Jan 23, 2003 7:56 am

>>> From: "Christoph Wels" <wels@infomine.com> 01/22/03 03:49PM >>>
Dear Jirka:

I am modeling the "draindown" of a tailings impoundment before and after cover placement and have the following questons on the HYDRUS capabilities (all related to output capabilities) :

1) How can I extract instantaneous and cumulative outflow for a user-defined section of the model boundary? The default output options in HYDRUS (Q vs time) only seem to provide the total (net) flow for a given type of boundary condition (say constant pressure or seepage face). This causes problems if I have the same model boundary type at various model boundaries. For example, in the case of a simple column model where a constant pressure is specified for the top and bottom boundaries there seems to be no way to get the inflow into the top and outflow at the base as separate outputs. Do you know of a way to extract such information quickly using HYDRUS or the WMS output files?

2) A similar problem is encountered when I want to know the water (or solute) flux across a user-specified section (line segment) in the interior of the model. Is there a simple way to extract such an nformation from the output files provided by the model?

3) I have also tried to extract information about simulated water flux
across a section using subregions (perpendicular to the direction of low) and looking at the water balance. Unfortunately the water balance only seems to give me only the net flow (=outflow-inflow) across the entire subegion. Is there a way to extract a complete flow budget for a selected region (e.g. all inflows and all outflows as provided by e.g. MODFLOW in its FLOWBUDGET module)?

I would appreciate if you could help me with those queries.

Best Regards,

Christoph Wels Ph.D., M.Sc.
Principal Hydrogeologist
Robertson GeoConsultants Inc.

Jirka
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Post by Jirka » Thu Jan 23, 2003 7:58 am

Christoph,

1) You are right about the reported fluxes. They are only for the entire boundary of a particular type. There is, however, possible to get actual fluxes across any boundary nodes from the output file boundary.out. There you can just select nodes in which you are interested and add Q values (e.g., in Excel). If you need I can add to this file also solute fluxes (Qc).

2) I have developed a special version that can calculate fluxes across specified cross section. This part is however not supported by the interface and user has to manually describe the cross section (nodes and elements at the cross section). In principal this should be applicable also to boundaries, but I have not tested it for that. Let me know if you are interested in this option and I will send you instructions on how to do that.

3) Unfortunately there is not such information and I do not know about simple way of getting it.

Best Regards

Jirka

Dapul
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Post by Dapul » Sun Jan 26, 2003 2:47 am

Dear Christoph and Jirka,

I have been using v.out and conc1.out files to extract flux information across a boundary. I import these files into excell and use macro-visual basic to extract the velocity and concentration at the nodes that I specify. It does this for each time. Then i multiply the concentration with velocity to get solute flux. Christoph if you are interested i would be happy to send you the code, it is pretty basic. Jirka, if you see any problems with this approach that i may not be aware of, would you let me know?

Defne

Defne Apul

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Post by Jirka » Mon Jan 27, 2003 1:13 pm

Defne,

Your approach captures only part of the solute flux. Solute flux is composed of two parts - convective and dispersive flux. Your approach handles only convective flux and ignores dispersive flux. Your results should be more or less the same as reported fluxes on the outflow boundaries, where only convective flux is allowed. However, on inflow boudnaries, or inside of the domain, dispersive flux can be important.

Jirka

jkrivic
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Post by jkrivic » Thu Sep 08, 2005 11:26 am

Dear Jirka,

I’ve incountered the same problem.
I am trying to evaluate fluxes across various boundaries of the same type. My initial idea was to plot a graph of velocities across a boundary and integrate the area thus obtaining flux. However, I have noticed, that when plotting such a graph for a no flow boundary I do not get a “no velocity” boundary. I assume, that the plotted velocities are the absolute lengths of velocity vectors and not just the vector components perpendicular to the boundary. Is this true or am I missing something? If this is true, than this approach would be wrong.
Are the velocities written in v.out the same values (absolute lengths of velocity vectors)? If so, the solute flux calculation from v.out and conc1.out values is also questionable.

How could I obtain the version that can calculate fluxes across specified cross section?

Regards,
Jure Krivic

tmalmir
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Re: Boundary fluxes

Post by tmalmir » Wed May 09, 2018 9:18 pm

Dear Jirka,

I am using Hydrus-2D to simulate infiltration to a lysimeter. I can have boundary flux (cm/day) by choosing infiltration result. But it is unclear to me how to get internal fluxes in several sections of my lysimeter. I would appreciate your guide, if possible.

Thank you
TM

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Re: Boundary fluxes

Post by Jirka » Wed May 09, 2018 11:04 pm

HYDRUS uses Meshlines to calculate fluxes anywhere in the domain (as well as anywhere at the boundaries). However, I'm not sure if this feature was available already in HYDRUS-2D. Likely not; it was likely introduced with later versions of HYDRUS (2D/3D). J.

tmalmir
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Re: Boundary fluxes

Post by tmalmir » Mon May 14, 2018 6:17 pm

Thank you so much for your reply Jirka. Please kindly be informed that my program version is 2.05.0250 with release date 7.3.2017. I do not know how to find flux (e.g. cm3/s) for internal sections of my lysimeter and I would appreciate your help.

Thanks
TM

Jirka
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Re: Boundary fluxes

Post by Jirka » Mon May 14, 2018 8:35 pm

Meshlines and their use is described in both the user manual and help. I do not have much I can add to it. J.

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