Flexible Gate

Hello all,

I've been playing with the Flexible Gate example. I created a 2D channel and hinged it to the upper boundary, then added in/out layers and it seems like it's working.

However, when I try to make the channel height and the gate height smaller, all the floating objects float freely and eventually leave the domain.

I created new id's for each block thinking that would be the problem but it did not help. When I run the same xml file with a bigger domain it works. I don't think it's normal but I might be missing something.

Thank you!


  • I tried it using a single block with 3 different domain sizes.
    Domain 1 has the exact same dimensions as in example flexibleGate.
    Domain 2 is the intermediate case
    Domain 3 has a channel height of 30 mm with a gate size of 13mm.

    Domain 2

    I'm limiting the domain size as follows

    And it works for domains 1 and 2, but for domain 3 I still get the following error

    Whenever I try to use a smaller domain, I can't get it to work.
  • When I increase the thickness of the gate, I still get the "particles excluded" error but nothing about the particles exceeding the simulation limits.

  • So, I still have been trying different dimensions and resolutions.

    x is the gate thickness .

    i)When I take the particle spacing to be 5e-4, it works for a gate with 60mm thickness.

    ii)A gate with 10,20,30mm thickness and 2e-4 initial spacing gives me error.
    When I increase the thickness to 40mm with the same initial spacing(2e-4) it works.

    iii) When I reduce the initial spacing to 1e-4, it still does not work for a gate with 10,20mm thickness but it works wen the gate is at least 30mm thick.


    i) It works when the number of particles is at least 120.
    ii) It only works when the number of particles is at least 200.
    iii) The minimum required number of particles for this resolution is 300.

    I think I am lost. I will keep trying and updating.

  • I hope you figure it out, seems to be an exciting project! Have you tried using the fixed domain command and ensure that it has like 0.5 m on all sides? Maybe that could help?

    Kind regards
  • @Asalih3d I've tried to limit the simulation domain with +-0.5, +-20%, +-50% .

    The error message reads
    "Excluded for: velocity"
    But in this post https://dual.sphysics.org/vanilla/discussion/1586/motion-error/p1
    it says "Excluded for:position"
    Maybe that tells me something.

  • Hello again,

    I'm still trying but no luck yet. As written in the previous post, the error message said " Excluded for velocity", so instead of using in/out layers, I decided to give it a try with constant acceleration in x-direction just like is Case/Poiseuille, the error message still reads excluded for velocity and when I open Error_boundaryOut.vtk this is what I get

    Light-colored region is the fluid domain and the blue rectangle is the gate, I don't know why there is a void region inside the gate and what is causing it. This is the case where the gate is 5mm thick.

    When I reduce the thickness to 1mm, I get rid of that void but the gate moves out of the domain, I really don't know why it doesn't stay hinged.

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