• Calibration of User Data Parameter

    Hello all,

    i am working on a 2D flow and transport model. I have set different recharge zones throughout the model's surface by using the [b] (flow) Source/Sink parameter.[/b] Then, considering the water flow input in each element, I have created a "User Data" parameter, that represents the [b]concentration[/b] of the water entering the model at each element. Finally, to calculate the total mass that enters the model at each element I have used the expression editor to assign the result of the [b]product[/b] of the [b](flow) Source/sink[/b] value times the [b]concentration[/b] to the [b](mass) Source/sink[/b] property.

    At this point, I wonder if there is a more straightforward way to create this BC.

    The problem I have is that I would like to calibrate the value of the Concentration, but in PEST it has no effect, as I understand that the expression used for the [b](mass) Source/sink[/b] is not "linked" and it doesn't change automatically when one changes the value of Concentration.

    To clarify, I have around 20 different zones for [b](flow) Source/sink[/b], 5 for [b]Concentration[/b] and it results on more than 70 different values of [b](mass)Source/sink[/b], so It is very time consuming to do manually.

    Thank you very much,
  • Coordinates numerical error

    Hello all,

    I am working with a box model I have created by using the F2 option to input the coordinates (x,y) of the domain as follows: (0,0) (2,0) (2,1) (0,1)

    Later, I extend the mesh with the 3D Layer Configurator. I use some 2D lines to check the model results, some of wich are along the model borders (I also used the F2 option to input its coordinates). See first picture.

    The problem I am finding is that it seems that at some point, the coordinates at the borders are slightly changed. If I try to make a node selection using the expression editor (e.g. x_global=0), the border of the model that I would expect to be selected completely, is only selected irregularly. To fully select that border, I need to write in the expression editor x_global<0.001.

    Also, when I try to plot the data-trace along a 2D line placed at the border of the model, the data plotted is discontinuous, as if some parts of that line fell outside of the domain boundaries. See second pic.

    Am I doing something wrong? Thank you in advance.
  • Re: Coastal aquifer: 3D density variability

    Thank you Durchlassigkeitsbeiwert,

    I am trying the ideas you proposed I'll be updating on my advancings.

    Meanwhile, does anyone know of other seawater intrusion 3D models that may serve as a reference to build mine? Any documentation on numerical criteria for this density-driven type models?

    Also thanks for the additional notes. I want to clarify that I used the "saltwater head" BC option on the seaside.

  • Coastal aquifer: 3D density variability

    Hello all,

    I am working on a coastal aquifer 3D model, for wich before getting to the model itself, I am doing some previous simpler models in order to gradually understand the process before getting to a more complex model.

    I am having problems to model a very simple variable density 3D model. It consists of a rectangular mesh with 6 Layers (1000x2400x45; length perpendicular to the coastline x length along the coastline x depth). Everything is fine if I run the simulation with a density ratio of 0 (i.e. without considering density variability), but once I apply a value of 0.025, the head and concentration distribution calculated are senseless (i.e. orders of magnitude without any sense like e+12 for the head ).

    The BCs I apply are:

    - Constant Saltwater Head at the seaside boundary
    - Constant Flow (Neumann) at the inland boundary.
    - Constant concentration (35g/L) at the seaside boundary. I apply a min-mass flow constraint of 0, in order to desactivate the BC where water flows out of the model (i.e. the shallow part of the boundary)
    - Constant concentration (0 g/L) at the inland boundary.

    Thank you
  • Re: Coastal aquifer: BC seaside

    Thank you Peter, that's exactly what I needed.

    I was sure there had to be an easy way for implementing that kind of BC.
  • Coastal aquifer: BC seaside


    I am working on a model of a coastal aquifer using the sea as a boundary. The model is a 2D cross section, similar to the Henry problem and considers density variations.

    The model flow BCs consist of a constant flow (Neumann BC) entering the model through the inland boundary, and a constant head (Dirichlet BC) along the seaside border.

    For the mass BCs, I want that any inflow produced in the seaside boundary has a concentration of 35 g/L (saltwater), but any outflow has the ambient concentration of the aquifer fluid.

    I thought of evaluating the fluid rate budget at each node, and assign a value of the concentration depending on its symbol (using an if function), but this option does not exist in the expression editor as the rate budget is not available.
    Any ideas would be greatly appreciated!

    PS: I don't know (yet) how to script using python
  • Re: 3rd type boundary conditions


    I am also having a similar problem (see pictures attached)

    I have set different 3r kind BC (Cauchy) in a 3D model (on the top slice and with all the nodes in the river's vicinity selected). All the condition are suposed to be an exit of the model for the water: so the in-transfer rate is set equal to 0, and the out transfer is set to a positive value.

    What I find in the rate budget is that there is a very high value for both in and out rate on the Cauchy BCs bar. The difference between these values is sometimes an exit rate that I could interpret as the real water leaving the model in that area, but many other times it just doesn't make any sense... I really need to understand how much water is leaving the model to validate it.

    Also, by checking the head distribution it doesn't seem that there is any place where the water is entering the model through the BC.

    Thank you very much,


  • Re: 3D unstructured mesh from Leapfrog Geo

    Thanks Peter,

    I have solved the problem with the intersections now and I managed to generate the fully unstructured mesh directly from the Leapfrog Geological Model. The problem I have now is that the mesh consists of about 7 Million of elements, of wich 4.5 Million have a volume of 10 m3 or less (and 4 M, less than 1 m3).

    To fulfill my purpose, I do not need such a fine resolution (except for some specific areas around wells, 10^6 m3 would be generally OK). Is there any option to generate the mesh with more flexibility so I can control the minimum volume of the elements?

    Anyone understands why do I get so many, and so small, elements?

    Thank you

  • 3D unstructured mesh from Leapfrog Geo


    I have currently built a 3D geological model using Leapfrog Geo 5.0. I aim to create an unstructured 3D mesh in Feflow using the GM exported from Leapfrog (*.lfm), which consists of 6 volumes corresponding to the 6 diferent lithologies.

    When I try to generate the unstructured mesh using "Supermesh import from maps", if I import the complete model (as 6 volumes-contact surfaces) , I get the following error from TetGen:  "[b]Tetgen meshing error: A self intersection was detected[/b]". If I import just one of the volumes (from a separate *.lfm file) the error disappears and my unstructured mesh is generated, obviously just for the volume that I have imported.

    How can I adress it in order to generate a mesh for all my domain, including the 6 lithologies?

    Also, once the mesh is generated, is there an easy way to select the elements that correspond to one lithology? I am thinking of groups of elements in the selection panel generated automatically from de *.lfm input file.

    Thank you,