I've got a question regarding local groundwater infiltration. I am working on a horizontal 2D-model for simulating heat transport in the saturated zone. For this model I want to implement a local source of groundwater infiltration. The water is hereby not injected through a well respectively a single node! It is furthermore infiltrating within a specified local area that contains a variety of nodes. To characterize the infiltration I prepared a time series of flow per area and its corresponding temperature. There are periods in which no infiltration appears at all.

Both, the infiltrating water and its corresponding temperature, I want to define for a local area in the model. I thought of the infiltrating water as a source that is mixing with the groundwater. Both temperature signals, of the infiltrating water and the groundwater, are supposed to be mixed, resulting in a characteristic temperature plume. I tried a couple of things, but didn't suceed.

It seems that FEFLOW is working with a fixed reference temperature that is automatically applied to the water source. That leads to the following question:

How can I link my temperature signal to the infiltrating water flow?

I am grateful for any kind of help.
Dear Mandy,

If you are using a material property to provide the infiltration, FEFLOW will take as temperature the reference value imposed in the Problem Settings.
Instead, you could combine a Fluid-Flux BC for the flow part and Temperature BC for the heat part. In a confined aquifer, the Fluid-Flux BC is expressed in m2/d.

Regards,

Carlos
Depending on the relation between infiltrated water and lateral groundwater flow, in such a 2D model a temperature bc might lead to an overestimated impact of the temperature of the infiltrating water (all water passing these nodes will get this temperature). The only possible alternative is then the use of heat-source boundary conditions, calculating the source in advance. Please note that for this option you will need to use the divergence form of the heat-transport equation, so that the  heat-source BCs describe the total heat flow, not only the dispersive/diffusive part of it.
First of all thanks a lot for the quick answer!

Yes, the temperature bc would also fix the temperature of groundwater at this point. And it leads indeed to an overestimation, especially in periods of small infiltration volume.

Though I have some more questions regarding the suggestion of Peter. What exactly do you mean, when talking about a heat source bc? Is it heat flux bc or is it heat source in material properties? I thought for such a model you need to work with source and sink term in material properties rather than a boundary condition?

Furthermore I am not quite sure how to correctly calculate the source in advance. This seems to be a little tricky. Could you explain this further?

As you said there are limited options. But I wonder, isn't there any kind of plugin available that might be able to solve this?

Regards,
Mandy

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