Cappilary fringe running dry

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janite
Posts: 11
Joined: Wed Jul 07, 2010 7:20 am

Cappilary fringe running dry

Post by janite » Tue Nov 15, 2011 10:12 am

This question is not specificly about Hydrus 2D, I have experienced the described effects with other programms, too.
I have recently tried to built models, that are quite big. This specific one is 150 m wide. (loamy sand, atm. BC at top, groundwater table at bottom, IC -500cm in the soil) It appears that when my mesh- elements are too big (~4m side length) my capillary fringe runs dry. Already in the first time step you see the elemtents above the groundwater table being extremtly dry. (see picture at the end) Also the Outflux is very much influenced as it shows huge volumes of water flowing out of the model at the very beginning.
I know this can be prevented by choosing a smaller spatial descretization. Therefor I am not looking for a solution to this.
I am interested however in how this effect is called and what causes it? Has anyone experienced it or can suggest some literature?

Thank you, Jana


This would be a picture of the situation:
Image

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