• Re: Unconfined vs confined vs semi-confined...


    I had this problem many times. For these cases I always run my model considering confined aquifer. Anyway, your hydraulic properties will ''guide'' the model.

    Take care if you use Free and movable because surface layer will change of shape after a run. You will agree than the topography cannot move in the real world.

    I suggest you to try several run with different settings with a transient setup. It generally help to reach the convergence.

    Good luck,

  • Re: Backward transport problem

    Ok I see, but can we ''play'' with lateral and longitudinal dispersion in order to eliminate this effect ?

    I have 2 tracer tests to compare the simulated and measured tracer BTC.

  • Re: Backward transport problem

    Wou ou,    :o

    It works pretty well, and the number of iteration required to reach the convergence is smaller. Can you explain to me the reason ?

  • Backward transport problem

    Hi everyone,

    I'm running a large model with steady flow and transient transport. For the transport, I'm using a reverse flow field and I'm simulating transport in backward from 7 pumping wells in order to estimate the contributing area of each well.

    Feflow allow an easy convergence of flow but the transport result is an horror. There's many log messages during the run indicating error with BICGSTABD (default) over than 1 e60. Results are incoherent with positive values and negatives (-1e60; 1e60).

    I'm using a consistent mass and convective form of transport.

    What can cause this problem ? Good idea is welcome because I'm trying different scenarios and it takes over than 12 h for each run.

    Thanks, Michael
  • backward transport simulation


    Someone know how to make a backward advective-dispersive transport simulation.  My goal is to define the contributing area of a well using dispersive properties. Because of this, I don't want to use the backward particule tracking (advective properties only).

  • Negative concentration


    I'm running a transient flow/transport model. So the borders of the contamianation plume are negative in mass. This situation is obviously impossible. Why this results and how to resolve this problem. If I have to put a constraint, please specify wich one.

    Thanks ,

  • Re: Element distorted


    Just another information. I modified my 8 slices to a constant elevation in all the model and I tried to run it. As I supposed, it worked well. It's just confirm the problem. Before to re-arrange my slices profile, I will wait for your advice ....

    thanks, Michae;
  • Re: Element distorted

    Thanks Peter for your answer. Just another question.

    With your answer, I supposed that the problem is caused by an important topographie on the roc body and by really thin layer superposition (8) in this section. Feflow indicate a mesh located in the center of a superelement. Beacause of this, I supposed the problem is not caused by superelement overlap. So, for all layers topography, Feflow must ''adapt '' the mesh in order elimate gap in the layer.

    There is rule of tumbs that we should follow in order to eliminate this problem.....because I have to modify the model layers topography ?

    Thanks, Michael
  • Element distorted

    Hi everyone,

    I have a really big model with 434 546 elements. When I'm trying to run the model, there is an a pop up window indicated :

    Non positive determinant for element = 1947. Obviously, an extremely distorted element geometry as a result of false mesh design an generation.

    I really dont know what to do with it . It fact, mesh generation is performed by FEFLOW and it autodetect a problem. How can I do to correct it considering that I have 434 000 elements....


  • Re: mesh generation

    Thanks Peter,

    A little advice for other user. Mesh generation is frequently interrupted because ''add-ins lines''. If you have an important model with many rivers (50-100) it's difficult to pass all nodes and lines with superelements borders.

    If you use MAPINFO, you can genrate points conresponding to lines at each nodes of the line. You can also generate points at a specific distance on the lines. After, you just have to use ''add-ins points'' with the nodes corresponding to river lines.

    The result is not perfect but pretty closed to river lines. So it's more simple and it allow's us to save many time.