transient imbalance

Hello everyone.
I'm new user of Feflow, I am not sure about using the transient imbalance for the phreatic method.

I have noticed high flow imbalance errors in each time step. However, these high values do not impact the results of flow rates in hydraulic head bcs and calibrated levels. Could someone explain me what that means?

I also noticed that there are in and out flow for the Internal Transfer (Discrete Features), however I didn't use any Discrete Features when modelling. Why this is calculated?

Hi Leo,
I guess your elements selection has multilayer wells(MLW)? Because each MLW is internally composed of a 1D Discrete Feature (DF) + one Well BC.

Hi Jintao,

Thanks for answering!

Yeah, correct! There are some MLW in my elements selection. However I still do not undestand how MLW impact in high flow imbalance errors in each time step.

Do you know or have an idea about what that means?

Hi Leo,

It is hard to say without knowing the details of the model. Which solver are you using? How is the quality of your mesh? It might be even due to the inappropriate temporal and/or spatial discretization.

Please refer to the online help:

"The respective fluid, heat, or mass balance is subdivided into flows related to the various boundary-condition types, contributions from distributed sources/sinks (e.g., groundwater recharge), storage capture (negative) and release (positive), and a remaining imbalance term arising from solver resid­ual error and errors due to the spatial and temporal discretization."

(http://www.feflow.info/html/help73/feflow/11_Results/Budget_Analysis/budget_analysis.html)

If you need a further check of the model, please directly contact our support(mike.de@dhigroup.com) to send the model.

Best,
Jintao