Dam break 3D tutorial

Hello all,

Just started with DualSphysics today. I am using the DesignSphysics addon with FreeCAD.

Super amazing tool and interface. All thanks to the developers for keeping it open source.

I have a question regarding the tutorial. Please see the attached figure.

The dam break seems to have some issue. There seems to be a jump in particle at the bottom. Why is that so? Is that an issue with my setup?

Can someone please help?


  • Hi,

    It's perfectly normal. it is a side effect of th boundary formulation.

    See FAQ 13, https://dual.sphysics.org/faq/#Q_13

    Water is instantiated without it, but when it flows it appears.

    Best regards

  • Hi,

    Many thanks for responding.

    Does this mean that we are using something similar to the no-slip boundary condition on the side walls? I tried increasing the particle distribution ~ reducing the dH. Even then, the spacing is the same. Please see the attached figures.

    I am interested in exploring boundary interaction physics. Please let me know if cannot use the model for this purpose.

    Thank you and best regards.

  • You should use the new boundary conditions, named "mDBC".

    To use them you have to stop using DesignSPHysics and work directly with the full package available at: https://dual.sphysics.org/downloads/

    There are many cases you can follow in DualSPHysics_v5.0/examples/mdbc

    You can also read the new paper: English A, Domínguez JM, Vacondio R, Crespo AJC, Stansby PK, Lind SJ, Chiapponi L, Gómez-Gesteira M. 2021. Modified dynamic boundary conditions (mDBC) for general purpose smoothed particle hydrodynamics (SPH): application to tank sloshing, dam break and fish pass problems. Computational Particle Mechanics. doi:10.1007/s40571-021-00403-3.

  • Dear Alex,

    Thank you for the input. I will try that option. I have a follow-up question here. Please see the attached video. Is this issue also due to the boundary conditions?

  • No, that is not related with boundary conditions...

    However I can only see an image and I do not know what is happening there.


  • Hi,

    Try to visualyze the actual boundary particles (in simulation folder bound.vtk). From my experience, it could be from the "staircase" effect (see gencase).


  • That can not be a staircase effect... perhaps a mountain effect ;)

    However the suggestion is good: please plot Case_Bound.vtk


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