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?

Comments

  • 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.

    Regards

  • 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).

    Regards

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

    However the suggestion is good: please plot Case_Bound.vtk

    Regards

  • Hello,

    I am sorry I couldn't get back to it earlier. I would like to thank all of you for pitching in.

    I have a few observations

    1) I am using the designSphysics module integrated into the FreeCAD for my simulations.

    2) @Alex and @TPouzol One of the issues, (the one similar to fluid jump) is caused due to staircase effect. The automated particle distribution within the freecad module distributes particle horizontally, thus causing steps (unintentional) (please see the attached snapshot). I was wondering if there is any workaround other than reducing the interparticle distance.

    3) There is a 3 layer gap between the wall and water, why is that? is there a way to reduce/remove that? Is this somehow related to inter-particle spacing? or using ghost particles for pressure corrections?


    Right now, my inter-particle distance is 0.005 m and I can go up to 0.001 m. Please let me know your thoughts. I will post an update when I finish the simulation. Thank you


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