2D Vertical Model, unsatured, pressure calculation

hi,

I have created a 2D vertical Model with boundary condition of 1st kind (head) at each side.
It runs and converges well.
I have good results for heads,
But When I want to see the result in pressure, I get some very high value (like 100exp4 kPa). I want to see the aquifer level by displaying the line of pressure=0 but it doesn't work....

Can you help me ???

thanks

florence 

Hi,
you should check 2 things:
- Have you defined the model to be an unsaturated one (in problem class menu)? Otherwise there will be no free surface in your computation.

- You should check your coordinate systems (whether the local one is equal to the global one). This is important because the values you define as BCs are related to the LOCAL system (I have no idea why they still use this in vertical 2D models).

Zebra

Thank you,

it's ok for the first thing : the model is defined as an unsatured one

But there is in fact a big difference between the local and global corrdonnate system.

the model vary from 30 to 45 meters above sea level in vertical in global coordinates.
and I have affected a value of 40 meter for my 1st BC.

BUT the local ccordinate system gives me coordinates around 1200 meters.

so if I understand well, I should apply a correction on my head-BC to translate them in local coordinate system ?

can you confirm me that ?

Florence

Hi Florence,

you should shift your local coordinate system to the global one. Then this problem should no longer occure. (Tanslationof your Head-BCs into the local system would also work, but this makes a model a little bit obscure).

This shifting is not very straight forward (I like to call it a graphical voodoo procedure...). You can find an explanation video on the  FEFLOW support site (http://www.wasy.de/deutsch/produkte/feflow/support.html), look at the "How to's" on the bottom of the page and have some fun with it.

I asked the devellopers several times to get rid of this nasty thing. I would appreciate it if also some other people ask the FEFLOW crew for some change in this point. Maybe this would help. I can see no reason in this, and it is an error source, especially if the difference is not so big as in your case you may accept some wrong results.

Hope this will save your problems,

Zebra

Perfect,
Thank you very much.

I have already made several 2D vertical model without detecting the problem (probably because the differnece of coordinates system was not so big, as you say)

and I am quite angry because probably my results were wrong,
Of course I wil complain, because it's quite amazing that you have to discover this erros source. There should be at least  warnings in the user manual, untill the developpers do something for that

thanks again

best regards.

florence