psinton@aquageo.us

Hi Mark,  Its not clear to me how you've determined the ideal element size, but you can test the effect of lateral spacing of nodes by reducing that spacing. The simplest way would be to add elements around the column of pumping nodes.  If the simulated water level at the pumped node is significantly different, you know the spacing is important for computing that water level (and water levels near the pumped node). You can make the elements as small as you want...the element size relative to the physical size of the well is not so important to this test. 

Vertical spacing tends to be less important horizontal spacing due to smaller induced vertical gradients. 

You can also add the user data distribution $error_norm_flow (look for "predefined distributions" in the help). After you run the simulation, this data distribution is the computed error at each node in the model.  You may find that the pumping node has the largest error and therefore the least accurate simulated water level.

Pete

In BoreTest.fem, the horizontal node spacing next to the pumped node is about 1 meter, and the vertical spacing is 50 meters, which is probably too large to allow accurate simulation of gradients near the pumped node. Another consideration is the hydraulic conductivity. If its small relative to the pumping rate, any simulator will have trouble with convergence.  So make sure the grid spacing is sensible and that the K is compatible with the pumping rate.  If you're not using automatic time stepping, smaller time steps may also improve convergence.

I suggest you run a test on BoreHole with a lower pumping rate or increased K. If the odd results disappear, then you know there is something about your model that needs work.

Another observation about BoreTest: the geometry of a few of the elements near the pumping node are less than ideal, which may contribute to numerical instability.

Pete

This is not a bug. Switch it back to the other mode to stop the "automatic recharge".

Pete

You can specify time steps to save in addition to the steps computed via the automatic stepping. Simply specify that feflow save all time steps including specified ones, for example at the end of day 1, end of day 2, etc.  Feflow will automatically insert these specified times into the time stepping sequence so that you can use the resulting dac to compute daily budgets that are not missing simulation data. However, you would still have to do some filtering of the resulting output to list only the budget information at the end of each day. See screen capture.

Pete

If you are using version 6, look for "temperature" under "heat transport" on the data panel. You should be able to set initial temperature of the water by selecting all nodes and setting the temperature at them using the input box, just like you would do with any other nodal value.

Pete

you could probably do what you need via "user data" distributions

Pete

reply to KC: an article in english attached

reply to Mark: I wonder if you have a timing problem in which the K and S of the pit are increased too soon. Consider using more gradual changes in K and S, and remember that FEFLOW averages material properties over time, so that for a simulation time step that falls between one value of K and another, FEFLOW computes an intermediate value of K that is a linear interpolation between the two specified K's (this depends on which averaging method you choose, and the averaging approach applies to all materials).

Pete
www.aquageo.com

another possibility is to use an element selection that excludes the elements that you want to be invisible. When you activate such a selection, and then add to any view the element data you want to see, only the elements of the selection will be shown.

There are numerous things that could be the problem, and without more information, advice might not help.  Is the model transient or steady-state? what mode are you running...confined, phreatic, variably saturated? What are the other boundary conditions in the model (in/outflow on top/bottom, wells, etc)? What is the initial head of the simulation?

Pete

Another option is to export the resulting heads to a dat file, then use that exported data to set the hydraulic head distribution for the transient. If you save the fem, be sure to give it a different name or you will overwrite your steady state fem.

Pete