Fluids

Fluids

What does the DPM/MPM ‘trap’ BC do specifically, & how does it differ from ‘particle deposition?

    • mcgrat25
      Subscriber

      I am running an MPM simulation in which I am trying to get a particle in a pipe to block an extruded 'leak' section by becoming fixed over the leak position. The particle is drawn to the leak by the pressure differential created by the 0 Pa pressure at the leak outlet (with 100k Pa inside the pipe). See below of a particle in contact with the leak:

    • Keyur Kanade
      Ansys Employee
    • DrAmine
      Ansys Employee
      Actually the DPM BC's do not apply. MPM is completely different as DPM and is an add-on module. What do you want to do?n
    • mcgrat25
      Subscriber
      I am trying to define boundary conditions that cause the MPM particle to cease motion as it comes into contact with the 'leak' outlet - its a bit hard to see in that screenshot, but this one might be a bit better:nThe reason I thought 'trap' applied to MPM, and not just DPM, is that I read somewhere that as MPM is an addon module, a lot of the settings within the user interface are not tailored directly for MPM, so state DPM but can be used for both. Given that the 'trap' option appeared when I activated mpm, I assumed it would be applicable to mpm.nIf trap doesn't apply, is my only option to use the particle deposition setting to stop the particle from moving? They don't seem to work for some reason, even when minimum detachment drag force is set very high and max velocities for deposition to be very low. I have an edge sizing of 0.05mm applied to the leak outlet at particles of 2.5mm, giving 50 cells at the point of contact (over the 20-30 minimum needed for MPM to predict drag), with -0.5m/s applied as the main pipe 'outlet' BC, 100,000Pa at the pressure inlet, and 0 Pa as the leak BC. The particle remains in contact with the leak when it reaches it, but moves ever so slightly every time step, so doesn't achieve a 'rest' state.nCan you think what the issue might be? Thanks again for the help.nn
    • DrAmine
      Ansys Employee
      MPM time step size should be choosen very carefully to resolve the particle wall collision. You might tune the coefficient of restitution to make the particle stick to the wall.nnYes it is built on top of DPM but has nothing to do with DPM. Actually even post-processing is made via text commands and you should not use the DPM Post Processing at all.n
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