Multi-sized Clump Spawning

[Dylan Stephens]

Hello,

I am trying to spawn 6-7 different clump sizes within the same sampling spawner (for example using sampler.SampleCylinderZ). The problem I am running into is collisions between the particles on the initial spawn causing a very large velocity. I have been messing around with spacing within the cylinder spawner, but I am mainly curious to see if there is a more efficient way to do this? 

I am aware of the method for building a terrain GRC-1 from the Chrono papers and demos, but I am curious if there would be a better packing method for the multi-sized clumps?

Thank you!

[Ruochun Zhang]

I think the easiest and fastest way is still to just use the largest separation, like you alluded to, if the clump sizes are not vastly different among them.

Unfortunately, I don't think Chrono or DEM-Engine has a readily available tool for what you are after exactly. But a more intricate sampling scheme is out of the core functionality of DEM-Engine as well. I can imagine an algorithm that does that: You first randomly (or follow whatever policy of your choice) pick clump types and store them in an array, then you know the axes-aligned bounding box of all the particles you want to create. Then if you also know the cross-section shape of the region you'd like to fill, this problem is a classic 3D strip packing problem. Then you can solve it yourself or use some tools for that, e.g., py3dbp, packingsolver. Again, this seems like a standalone problem to me, and we are probably not going to integrate something like that into the solver itself any time soon; so you have to integrate it yourself.

Thank you,

Ruochun 

[Dylan Stephens]

Thank you for the response! I appreciate the help, and will look into some type of 3D packing solving method.