fix rigid/small in LIGGGHTS 3.0.1

Submitted by zamir on Tue, 05/13/2014 - 08:26

Hi All,

Fix rigid/small behaves very differently than fix rigid in v3.0.1. It seems like rigid bodies created by fix rigid/small can exert forces on neighbor particles, but the rigid bodies themselves do not move at all. For some reason, it looks like bodies created by fix rigid/small are not being time integrated. In the source code, the integration schemes look the same... Anyone have the same experience?

FYI, my comm cutoff is large enough, I have tried several comm cutoffs with no change in results.

Thanks,
Zamir

EDIT: Attached a test case

I put videos of the test case on youtube:
Video of test case using fix rigid (behaves properly):
http://youtu.be/lmpR2TABFtY
Video of test case using fix rigid/small (behaves unexpectedly):
http://youtu.be/aWdSVxs1LjE

AttachmentSize
Binary Data test_case410.21 KB

zamir | Sun, 05/18/2014 - 17:08

`Hi All,

I've been trying to figure what is wrong here, but I am thoroughly stuck. I think it is a bug.

Zamir

zamir | Mon, 05/19/2014 - 05:50

I put links to videos in the original post which illustrate the problem. The two videos should look exactly the same, but they do not because fix rigid/small does not work properly.

zamir | Tue, 05/20/2014 - 06:23

Hi All,

I peeked into the source code a bit and I found a few interesting things:
1) fix_rigid_small.h is not included (#include) in pair_gran.cpp or fix_wall_gran.cpp. However, fix_rigid is included.
2) PairGran, FixWallGran, FixGravity, and FixTemplateMultisphere are not declared as friend classes in fix_rigid_small.h. It seems like they should be. Correct me if I'm wrong.

I hope someone can help me out here, or at least tell me whether I'm heading in the right direction...
Thanks,
Zamir

ckloss's picture

ckloss | Thu, 06/26/2014 - 12:09

Hi fix rigid/small is currently not connected to the granular features - use fix rigid instead

Best wishes
Christoph