zhengq

I did a 3D transient model with 9 layers. I placed seepage face on slice 8 and 1D discrete feature through layer 1 to 7 (the bottom of the discrete features are the seepage faces) to simulate dewatering wells. When I set the maximum time step size to 20 days, the results look reasonable. You can see a drawdown cone developed in three months from layer 1 to 7. But when I reduced the maximum time step size to 1 day, the drawdown cone is  very different- you cannot see a drawdown cone except on slice 8. What is the reason for this?

Any help is appreciated.

Quinn 

Hi,

when using in-/outflow on top/bottom to apply recharge (due to precipitation) to groundwater, what would happen if you apply the recharge to lake surface (constant head BC)?  Will it have any impact on the solution? Theoretically the recharge due to precipitation to the area covered by lake should be zero, right?

Thanks in advance,

Quinn

Hi,

For a transient modeling, can I make the seepage face transient (i.e., it is active for some time, but "switched off" for other time)?

Your help is greatly appreciated.

Quinn

Hi groundwater modelers:

A question for you all. If a surface water body is included within a model domain, people usually assign a very big hydraulic conductivity to it, assuming that this big hydraulic conductivity will make the resistance to groundwater flow negligible. My question is: Is a very big hydraulic conductivity, say 100 m/s, physically feasible? If we use the most common method to measure the hydraulic conductivity of a medium, I would guess the biggest hydraulic conductivity could be obtained if there is only one tiny smooth sand (and air so that you still think it is a porous medium in a limit sense) in the vertical column. what value of hydraulic conductivity do you think you could get for this medium?  sqrt(2*g*h)?

Any comments are welcome.

Quinn

I simulated four chemical species in a mass transport model. In "problem Settings", I clicked on " chemical species", and entered the four species. When I changed the sequence of the four species, however, the chemical reaction functions does not change accordingly. That is, the first species (previously fourth species) still depends on the other three species. etc.

This might be a minor issue, but it is better to improve it.

Quinn

For 2D axisymmetric model in FEFLOW, does it have to represent a cross section of a cylinder? Can it represent a cross section of a truncated cone (using a plane parallel to the lateral surface)?

Thanks,

Quinn

Hi Peter,

The paragraph below is extracted from FEFLOE Help files:

[b]In 2D horizontal unconfined and cross-sectional models, the flux boundary condition has the unit [L/T], defining an inflow of water across an area in a certain time: [L³/(L1*L2*T)]. Here, L1 is taken from the length of the line the condition is applied to, while ........ For cross-sectional models, L2 is assumed at unit length (1 m).[/b]

My question is:
1. Is L2 assumed at unit length (1m) for both 2D vertical plannar and vertical axisymmetric model? Then what do you mean by FEFLOW is formulated for 360 degrees?
2. After run the model, you click on rate budget, and get a value like 100 m3/day. Is this number for unit length at L2 direction for both 2D vertical plannar and vertical axisymmetric model?

Thanks a lot.

Quinn 

The following paragraphs are extrated from FEFLOW help file.
Could anyone explain what it means? When I applied multilayer wells to the model, I got this error information. I chose "repair", but it seemed that it did not work. I got some unreasonably high pump rate for wells.
 
[i][b]Conflicting boundary conditions and multilayer wells/borehole heat exchangers

Two repair modes are available:

Keep Boundary Conditions / Multilayer Wells / Borehole Heat Exchangers
Assign Multilayer Wells / Boundary Conditions / Borehole Heat Exchangers
[/b] [/i]

I used a 3D model to simulate how much water should be pumped out from each well (totally I used 11 wells as a first trial) to intercept contaminant from a dam. I set a pump rate of 720 m3/day for each well as a first trial. I used minimum hydraulic head constraint for each well. After the model is run, I checked rate budget and found that the outflow rate from well is 10^9 m3/day. How does this unreasonable number happen? I appreciate any help.

Quinn

For a 3-D model, I plan to place 10 pumping wells.
I selected join edge at 11 locations.
Then I activated "multilayer well" on "Data Panel", double clicked on the "multilayer well" in the Editor toolbar, and I got the Multilayer Well editor.
I clicked the button on the Multilayer Well editor 11 times to choose which well I would like to work on.
For each well, I entered the pumping rate, top and bottom elevation, etc. , and clicked on "assign".
Finally I found that all 11 wells have the data I entered for the last well.

What happened? I appreciate your help.

Quinn