Hi there, I was simulating a pseudo-2D particle dropping process using DEM method with 21.2 version.
There are 2 walls ( \ / shape) inside a rectangular region, so that particles would be blocked/collected by them and flow through the gate between them. But I want to replace these 2 inner walls with particles, I mean fixed particles that differs from those flowing particles.
How to define such kind of special fixed particles? Is it possible to realized by uding udf, OR other approaches? Thank you for your time.
2d_repose.mfx (14.0 KB) 2d_repose.STL (1.4 KB)
Dear all, you may use these 2 model files to run this case. And as shown in the figure, I would like to replace the red line symboled boundary with fixed particles, if possible…
If you have a particle_input.dat which places the particles in the correct location, with zero velocity, they should stay put.
And this is settable per-phase so you can define another interacting solids phase where the momentum equations are solved.
However this option is only available for the TFM model. If you need to use DEM, I think some code modification will be necessary.
It’s also possible that you could use a hybrid model where the fixed particles are TFM and the other phases are DEM. This is not fully supported, however.
Much appreciated Charles for the detailed explanation.
However, I could not find any tutorial for hybrid model, even for the latest version 21.4…
So it seems that using DEM together with setting up per-phase solids is a potential solution. And which code needs modification to realize this, the .mfx setup file or the original source code of the software?
Thanks for your time.
Please see this forum posting to see how to enable the hybrid model. Note that hybrid model is not fully tested, is not supported, and is in no way guaranteed to work. But you may be able to use a TFM phase for the fixed particles (with momentum equations disabled) and DEM for the other particles. It’s at least worth a try.
If you want to stick with pure DEM, you’d be modifying the source code, to keep particles in a particular phase fixed. This might be as simple as finding where the positions are updated and skipping this for a pre-designated phase, but there might be more to consider (conservation of energy and momentum, you have to do this in a way that’s physically reasonable)
Please take a look at the screwfeeder example. This one imposes a velocity to a group of particles to mimic a rotating screw. You can apply the same logic but setting the velocity to zero for your group of wall particles.
