2nd BC well as drinking straw

I just learned to use 2nd BCs to simulate a well in detail. So I designed a flux-pipe around a single node over two slices to simulate my well screen which ends in the middle of an aquifer. The half flux-rate represents the pumping rate on the outer flux-border. But there are still two open questions:

1) To avoid that the well takes effect as a drinking straw at its lower "open end" by the flux-rate of the inner border, I planned to set an extrem low conductivity to all inner cells of the flux-pipe to plug it. Is that the right way?

2) On which layer does a flux-border on one slice (or the lowest slice in case of multilayer-flux-borders) take effect? For to calculate the correct flux-area and rate, do I have to consider the distance to the nodes ahead or to those above or should I add the half of both distances?

Thank You for an answer!

Hi Mac,

1.) That's right, making the inner side of the well low-permeable will mostly prohibit well-internal flow. Just keep in mind that a too high parameter contrast can make numerical problems; I usually use a parameter contrast of 100 or 1000.

2.) The flux-value on an internal boundary is applied twice, but no direction is given for the flux (meaning that the water does not have to flow with equal velocity in both direction). This applies for vertical BC (within a layer) as well as for horizontal BC (between two layers). In your case, the water will most probably flow in one direction only, you should therefore apply half of the calculated value to the BC. Don't forget to check the budget afterwards.