Posted Thu, 17 Jan 2008 23:19:39 GMT by Duncon

Check it out, why is the drawdown varying as a function of the element size?
Posted Fri, 18 Jan 2008 08:35:58 GMT by Alexander Renz
In numerical models, the drawdown at point sources (like the well) is always dependent on the mesh discretization, whereas a finer mesh leads to a stronger drawdown.
The mathematical background is that, taking a single well with a constant pumping rate as an example, the well is defined as a point in space. Now, the constant flux has to flow through a zero area.
As a consequence, near this point, the velocity - and the pressure gradient - becomes infinite.

A very fine discretization will approximate this solution (showing a strong drawdown), while a very rough one will flatten this effect (lower drawdown)

--> In reality this is not happening, since the well in nature is not a point, but has a diameter. If you use an element size eqal to the well diameter, you get an approximation to the real drawdown. Note that this is no exact solution, since the element size does never meet the diameter.
Posted Fri, 18 Jan 2008 15:39:24 GMT by Duncon
Alexander, thanks a lot for that answer.

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