Budget zones
Hi, i need to define the water budget in the geothermal system that i´m modelling, so i want to know if it es possible to define budget zones in TOUGH2 like in other softwares (e.g. Visual Modflow).
Thanks.
Juan Cristóbal
3 replies
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Hi Juan,
I assume you define a "water budget zone" as a certain volume within the model domain for which you want to keep track of changes in the total amount of water. You would do that in TOUGH2 by setting SPHT for all materials that you do NOT want to be included in the global mass balance to a value greater than 10,000 (reduce DROK by the same factor to make sure the heat storage capacity is preserved, e.g., if the true rock grain specific heat were SPHT=1000 J/kg C, and the true rock grain density were DROK=2500 kg/m^3, set SPHT=10,000 and DROK=250). Then you can extract the total mass of water at any given output, and subtract from it the initial value (i.e., that at KCYC=0) to obtain the water budget. If you want multiple water budget zones, you have to repeat this analysis for each zone in a separate simulation.
In case you have iTOUGH2, you can simply define an observation for each water budget zone using command >>> CHANGE of TOTAL MASS of WATER, and specify as many water budget zones as you want in a single analysis.
Stefan
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Thanks for your answer, but really i want to define the water budget in terms of the mass flows that are entering the system and the mass flows that are leaving it, to verify that i reach a steady state. For example, in my model i have defined two boundary conditions for the source, one is a dirichlet condition and the other is a neumann boundary condition where i define a local recharge to the system. The sinks are defined by deliverablity wells, so i know the mass flow that is leaving the system after the simulation. I also know the flows given by the neumann conditions, buy i dont know the flow that is entering the model in the dirichlet boundary conditions. If i reach a steady state that flow is easy to infer, because all the other boundaries are defined by no flux (i dont have flow connections across the boundaries), so i want to obtain that flow in the output for any timestep including a large time where supossedly the model reach a steady state . I thought that the option FLOF would be useful but i understand that it gives the flux between two elements.
Thank you very much
Juan Cristóbal. -
Juan,
Well, all you need to do is sum up the flows across all the connections to your Dirichlet boundary elements (make sure you account for the sign convention). That will give you the total flow across this boundary, to be equal to the sum of your sink/source terms. Yes, you may need to write a little post-processing program (or again use iTOUGH2, which allows you to define coordinate regions to select all the desired connections).
Stefan