mDBC with imported geometry


the documentation on the mDBC explains how to generate normal vectors when the geometry is relatively easy. However, I am wondering whether there is a way to adopt mDBC also when the geometry is complex and imported through stl files. I am not able to generate the boundary surface at a distance of Dp/2 from the first layer of boundary particles. I would need to use mDBC rather than DBC because the simulation shows problems close to the boundaries. Maybe "boundcorr" would do the job as well, but I couldn’t figure out how to use also this with a complex geometry.

Thank you for your help.




  • We have not included examples with external geometries yet since version 5.0 includes only simple examples we know that work well.

    The problem with external geometries, such as .STL comes from how "good" the STL is built, which means no holes, proper normlas need to be defined, etc... In case you have an STL that follows those indications then you only need to produce a second STL (with AutoCad, Blender...) with all faces at Dp/2, therefore one STL is used for normals and the second one to create particles.


  • We will include examples of this in the next version. But as mentioned before the STL file should be consistent and well constructed, which usually happens only if the user created the STL.

  • Hi Alex,

    thanks for you reply.

    Ok, I will try to generate a second STL with all faces at Dp/2. Should I then first run GenCase just to create the boundary surface and then load this vtk.file when I execute GenCase again to create the simulation particles? Is it possible to merge these two steps and execute GenCase only once? If I draw the two stl files in the same GenCase execution using a resolution of Dp, won’t this cause that the boundary surface will touch the first layer of fluid/solid particles?

    Thank you for the help.



  • Dear Manuel_CFP

    You will load the two files in the same XML file.

    I suggest you to check our examples and the XMLGUIDEMDBC.pdf to understand this.

    You will use STL1.stl to save the .vtk used to create normals and you will use STL2.stl to create particles. So STL1.stl should be the one with faces at dp/2 far from STL2.stl


  • Dear Alex,

    ok. Thank you for the suggestions.



  • Dear all,

    is <layers vdp="0,1,2" /> for creating the boundary particles working with .stl files (which did not so far in my problem) or do I have to create a .stl cover and fill this up the boundary particles?

    THX in advance

  • <layers vdp="0,1,2" /> can be used with some "own" operations like drawbox, drawextrude, drawsphere and drawcylinder

    this is explained in page 58 of XMLGUIDEv5.0.pdf in doc/guides

  • Hi @Dominik ,

    I have a similar question when trying to import external stl files. For example I have a 3D solid created in AutoCad or rhino, and export it into a .stl file. The thing is that I want to "fill in" the solid and to have parallel layers, but "autofill" can't do that for complex geometry, at least from my experience.

    I think about importing multiple layers of "surfaces" to create particles, however, after importing surface.stl, the particles does not create a nice "layer".

    Any suggestions? Thanks in advance.


  • Correction: "autofill" works for complex geometry, but you will have to deal with the mesh/edges within the .stl file, otherwise it will go wrong.

    Sorry for the misunderstanding.

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