General head boundary/Head-dependent flux in FEFLOW?

Hi,

Is there a way of representing a general head boundary in FEFLOW? With finite differences I am familiar with the process of defining a head at a fixed distance beyond the boundary and a conductance term. Is there an equivalent in FEFLOW?

Thanks.

You shall define a transfer condition with a transfer rate. Thus you specify the head and, by the transfer rate, approximately the ratio between conductivity and distance from the head condition. Refer to the manual for a more accurate description.

Giovanni

Thanks Giovanni, I'll see if I can get that to work. 8)

In the end I didn't need to use this, but I have now arrived at a situation where I think it may be a better option than attepting to rebuild a complex model with a larger grid. However, I have been unable to get the boundary to behave as I want.

Is the head value that you set for the transfer boundary equal to the head that you would set 'x' distance away in a general head boundary? Or is it something else?

I tried this in a simple box (confined):
* K = 10 m/d
* h = 100 at one end
* transfer boundary 2000m away at other end with h = 0

I wanted the transfer boundary to act as a GHB with the head specified an additional 2000m beyond the model boundary, so the outflow transfer rate was set to be:
K/2000 = 10/2000 = 0.005 d^-1

If this worked as planned then would it be correct to assume that the head will be approximately 50m at transfer boundary? In my case the head had hardly changed at all across the model and was ~= 99.99m!! What am I doing wrong?

Thanks.

Silverbrook, please check the following:
- Have you input the transfer rate in the correct unit (1e-4 1/d)?
- If the box is 3D: Have you set the boundary condition to at least two neighboring slices to enclose the entire vertical element faces of a layer? - The transfer BC requires an area.