Flow out of the base of a hillslope
Hello,
I am attempting to model flow out of the base of a homogeneous hillslope using TOUGH2.
I have set a constant head boundary on both the uphill and lower hillslope edges and defined the upper layer as an open atmospheric boundary with no ability to transport the aqueous phase. I have also set the volume of the atmospheric, upstream, and downstream boundaries to 50 times the volume factor.
However, when running TOUGH2, I am receiving negative x_water_L and FLOW_L values. I suspect this might be causing the flow vectors to migrate upstream. Is this the likely cause, and if so, what steps can I take to correct it? Are there specific aspects of my model setup that I should check?
Thank you for your assistance.
JPM
8 replies

Increasing the volume of a boundary elements by 50 times is not enough if you want constant boundary conditions. You should use something in the order of 1.E+30 or more.
Is the plot representing steadystate conditions? It is strange that you get a sort of convective cell with water flowing back to the higher head boundary. The choice about fixing the P on two edge boundary elements rather than on the entire boundary column is strange.
And avoid the water to escape the groud level seems also a bit strange. I guess the P set on the inlet and outlet boundaries should give a water table below ground level.
You might reconsider the way you applied bondary conditions.
Alfredo

Jordon,
May be I missed something about the conceptual model on which your numerical model is based.
A graphical sketch of the conceptual model would likely clarify what you intend to model.
Then, if you can share your model, I can try to have a look. I still have to update PetraSim to the last version, so I can run the model only if it is made with the previous one.
Let me know.
Alfredo