Here is a link to my new publication on ordering in vertically vibrated granular rods. This work was featured on kaleidoscope section of Physical Review-E and appeared on front page of PR-E website. Here is a pic 🙂

http://pre.aps.org/abstract/PRE/v88/i5/e052203

The paper also details a method for tracking hollow rods in 3-d using X-ray Computer Tomography data. The tracking code was written in Matlab and requires Image Processing Toolbox. I’ll write a separate blog entry detailing the algorithm used for tracking rods in 3d.

Following were the main observations of this experiment:

1. Vertically vibrated Granular rods go to vertically ordered crystalline state.
2. Global ordering depends on aspect ratio of granular rods. Longer rods tends to form perfectly order crystalline states with hexagonal order in interior, whereas shorter rods tend to form more defects (regions of horizontally ordered rods).
3. The temporal evolution of ordering can be explained using a void filling model.
4. Using a point-correlation function we can show that extent of hexagonal ordering increases with aspect ratio of rods.
5. By adding more number of rods (than required to grow a perfectly crystalline layer) we can grow a multiple layer crystal. Though we observe that higher layer tend to have more defects. We attribute this to inefficient energy transfer from bottom of shaker to top layers due inelastic collision in intermediate layers.

If you are interested in this work but do not have access to Physical Review-E send me an email at VYadav@clarku.edu and i’ll send you a copy of this work.