Posted Thu, 16 Jan 2014 13:06:14 GMT by Lamm

Dear Users of FEFLOW model,
I have some questions when using FEFLOW 6.1 below.

Q1: In the model setup, the following data need to be inputted into the Domain as follows:

3rd BC for river: 1 year of Water level with 10 minute intervals (from 1.1.3012-31.12.2012).
1st BC for Tidal: 1year of Tidal level with 60 minute intervals (from 1.1.3012-31.12.2012).

Question: Whether the different interval inputs into the Domain will affect the Model results or not? In my opinion for 1 day simulation, the input of water level data of river include 6times x24h=144 values, while only 24 values of Tidal level input. How can the Model recognize these?

Q2: Groundwater level is observed with 30 minute interval. This means that measured data are obtained every 30 minute. How can I setup the time step in the Model so that I can obtain groundwater level results with the same interval as measured data?

Thanks in advance,
Posted Thu, 16 Jan 2014 13:09:06 GMT by Denim Umeshkumar Anajwala
In case you apply an automatic time-stepping procedure, it will make sure that all the time stages in the time series will be considered as time steps. This means that no time step will be larger than 10 minutes, possibly leading to long simulation times. Inputting water levels on a 10-minute interval will thus also ensure that you'll get output every 10 minutes.
Posted Tue, 21 Jul 2015 18:56:19 GMT by gautxo89
Here's my problem: I have a quite large (about 500000 nodes), 2 layer, transient model. The input variables that are time-dependent are recharge and pumpìng wells, both with monthly data.

When I start the simulation, the time-step length grows untill 0.0001 days but then becomes stable, making the simulation too long to run (10 years). The model converges, it does not report any error, so why doesn´t it continue rising? How can I accelerate it?

Posted Wed, 22 Jul 2015 17:00:41 GMT by Björn Kaiser
I suggest to update to the latest Patch 9. Patch 9 covers some improvements with respect to the time-stepping. You could also try to adjust some settings in the model (e.g. mesh improvement, applying the fully implicit FE/BE predictor corrector scheme).
Posted Thu, 23 Jul 2015 13:05:18 GMT by gautxo89
Thanks for your reply,

I've updated to the new patch 9, but still doesn't work. If I change the predictor-corrector scheme to FE/BE it gets worse...

The top slice is Phreatic type, almost every other setting are set as default.
There's no change in primary variables (Hydraulic head) during the simulation

Every suggestion is welcome

Posted Thu, 23 Jul 2015 17:46:06 GMT by Björn Kaiser
Is the vertical discretization fine enough? I suggest to introduce some slices in the “pseudo”-unsaturated zone. Go to the 3D Layer Configurator. If you choose an unrealistic high Distance (999999 m) FEFLOW will distribute all inserted slices equidistantly with respect to the elevations of the upper and of the lower slice.

You could also try to increase the residual water depth for unconfined layers in the Problem Settings – Free Surface as long as the imposed value fits to the hydrogeological architecture.
Posted Mon, 27 Jul 2015 12:56:38 GMT by gautxo89

Finally it worked when I changed both the residual water depth and predictor-corrector scheme. Now It runs perfectly,

Thank you very much for your suggestions

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