Beginner questions

Hi all,

at the moment im modelling a problem in near-surface geothermics. Unfortunately my advisors dont know the feflow-stuff very good and during my study we dont get enough information and exercise. So please excuse my beginner questions. And sry for my bad english, i try my best.

I try to set my geometry bevor planting my BHE´s. But i meet some problems. I got a saturated and an unsaturated zone. My model is 60m deep but the upper slice is about 62m over sea surface. The groundwater lvl is 22,17m to ground lvl. A friend of mine said i easily had to set two hydraulic head boundary conditions to get a groundwater flow direction, which should be W-E. So i would set the first BC on the W-side with a hight of 22,1m and the second on the E-side with 22,2m to get a W-E-flow. Is this assumption right? Or do i have to take 40,x m above sea surface in order that FEFLOW understand what i want? Does FEFLOW understand that my unsaturated zone lies above this 22m? I hope i can get my problem across to you guys.

My second problem is the soil temperature. How can i insert this the best way? My first thought was to set a temperature BC at the W-border. So my groundwater flowing trough the border and take this temperature. My annual average temp is 11,3°C for the soil. Or is it better to set an initial condition over the whole model? How do i set initials? Simply insert it in "process variables --> heat transport --> temperature"?

Which brings me to another point. When i set initials or boundarys, where can i see my inserted values? When i set material properties they are shown in the slice view (on top of the view), but initials and boundarys are not shown. So i dont know later which values i inserted for these.

I hope i managed to explain my problems to u understandable and that you have any solutions für me.

Kind regards, Michael from Germany

Hi Michael,

1st kind BCs are set as 'hydraulic head' in FEFLOW which means that - in your simple case - you set the elevation (ASL) of the groundwater table.

For soil temperature you should set the fixed T at the inflow boundary. If you do not set an initial temperature, you'd have to run the model until it shows a steady temperature distribution. So it might be more convenient to set the initials, too.

BC values can be visualized in two ways: Either you activate the value display in the View Components panel, or you use the Mesh Inspector. For learning such basic functionality, it might be good to go through the FEFLOW demonstration exercise once.

Good luck!
Peter

Hi Peter,

thx for your quick answer.

Ok, and setting elevation of the GW table means FEFLOW know that over this border i got an unsaturated zone, doesnt it? I´ve already seen the exercise on youtube, but owing the missing statements i dont understand every click they made. In the video for hydraulic head BC they mark the whole border (every slice), and set their hydraulic head value. But which value i have to insert? I tip the groundwater table hight, not the value over sea surface?
So i kill two birds with one stone. I got set my unsaturated/saturated zone AND i set the GW flow direction, am i right?

Ok so for soil temperature i´ll take the inflow boundary AND initial?

The Mesh inspector worked. In the tutorials i wondered what it is for. Thanks for that!

Regards, Michael

There's a step-by-step description of the entire demo exercise in Installation Guide and Demonstration Exercise on http://www.feflow.com/manuals.html.