Hi Ruochun, Thank you so much for your reply. I have been trying to reduce the bin size in order to try to resolve the problem. However, I keep getting similar problems until I reach a point where I exceed the maximum number of bins allowed. I have tried to minimize my domain as well to help with minimizing bin size. I got to a point where my domain is reduced to the very minimum and my bin size is set to be the smallest possible without exceeding the maximum number allowed. However, I am still having the same problem. Ex: "Bin 7 contains 357 triangular mesh facets, exceeding maximum allowance (256)". I was wondering about what it would cost to increase either the maximum number of meshes contained by particles or the maximum number of bins of a simulation.
About the mesh size, I am trying to verify my implementation of the cohesion model I implemented using this paper (Discrete element modeling of planetary ice analogs: mechanical behavior upon sintering | SpringerLink <https://link.springer.com/article/10.1007/s10035-021-01167-6>). In that paper, the cone has a small mesh (0.2mm) and the shaft has a larger mesh (2mm). However, the particle size is 2mm. Do you see any obvious problems with that? you mentioned that having a smaller mesh than the particles causes the forces calculations to be inaccurate. Could you please explain that a little more? Thank you so much for your help, I really appreciate it. On Friday, December 30, 2022 at 2:21:09 AM UTC-7 Ruochun Zhang wrote: > Hi Mohammad, > > *SetCDUpdateFreq *sets the maximum number of time steps by which the DEM > physics can run ahead of the contact detection. So naturally, if this > number is large, the contact detection subroutine needs to add a bigger > envelope/safety margin to ensure it does not miss a contact that can > potentially appear in the "future". That's why it is possible that when you > increase it, more geometries appear in one bin and potentially cause > problems, since the geometries here mean the geometries with the safety > margin included. > > But this should really be less of a problem for meshes, and I am a bit > surprised here. You know I wrote this error message, but I myself never > ever saw that in my simulation outputs. Meshes used in DEME are expected to > have triangles somewhat larger than the particles (if you do need the mesh > to represent geometric features that are smaller than your particles, then > the contact force won't be calculated accurately anyway, because your > particle shapes are approximations too), but it seems to be not the cause > in your simulation, as you see problems with the mesh before you see that > with the particles. If you just happen to be using huge particles (and > therefore comparably small mesh facets) for this simulation and you just > want it to run, then you can always use smaller bin sizes to resolve the > problem. > > As for what number you should use, this is hardware- and > problem-dependent. The target is always to use *the smallest number that > is able to minimize the times that dT is held back*. This means right > now, you have to try it out to find the best choice. I found with A100s > many typical use cases benefit from that being set to something like 20. > With consumer-grade GPUs, it tends to be larger, like 30 or 40. Just so you > know, if the sweet spot is 20, and you set it to be 5 for example, then you > are pretty much running at 25% speed; if you set it to 30 on the other > hand, you will be running at a slightly reduced speed but not too bad. But > a number too large has the associated risk of leading to too many > geometries in a bin. > > Now there is good news. After deliberating, I think I know a way to make > the bin size *and *CDUpdateFreq adapt automatically, and remove the limit > of the number of geometries in a bin, meaning when it materializes you will > no longer see this error again. If it does pan out, I'll let people know. > > Thank you, > Ruochun > > On Thursday, December 29, 2022 at 8:13:02 PM UTC-6 [email protected] > wrote: > >> Hello, >> >> This is DEME related question. >> >> How does the function SetCDUpdateFreq affect the maximum bin allowance? I >> have been running a code with SetCDUpdateFreq(6) and everything was working >> fine. However, when I changed the input from 6 to 15, I started getting an >> error saying that Bin 32 contains 264 triangular mesh facets, exceeding >> maximum allowance (256). Also, I am running a cone penetration test, does a >> value of 6 considered a low value for such a test? >> >> >> Thank you so much in advance, >> >> > -- You received this message because you are subscribed to the Google Groups "ProjectChrono" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/projectchrono/1750d511-e645-42c3-a0e7-b49cc38e0013n%40googlegroups.com.
