Measuring Packing fraction

Hi Joel,

you can e.g. measure #particles or mass for each group or region by using the variable command. ALternatively, you can use CFDEMcoupling for a detailed volume fraction evaluation. Or there is also the voronoii package available.

But I just realized it would be easy to add "volume" to the variable command. I'll do this for the next release

Best wishes
Christoph

hey there !!

When I insert a number of particles in a region whose volume is far greater than the total volume of the number of particles that I wish to enter using insert/rate/region command, it still does not enter all the particles and gives me ''WARNING: Particle insertion: Less insertions than requested". I worked around this problem by increasing the volume of the insertion region still further, and further, until all the particles were included. Why is this happening ? Is there a way to keep the volume of the insertion region constant and still insert the required number of particles ? Please help.

regards,

Anand.M
M.S. Mechanical Engineering
I.I.T. Madras

Hey guys, Is there a way to find out the height of the particle bed formed, after I insert the particles into the container. Like for eg. knowing the " z-coordinate(s)" of top most particle(s), so that I may calculate the packing fraction for that particular type arrangement of particles ?
Please help.

regards,

Take a look at the variable command and/or the compute reduce command (min/max functions).

hey Daniel, variable or compute reduce command is not serving my purpose, as I have to calculate the packing fraction after I have poured the particles in the container and they have settled and before my simulation begins. So, essentially I don't know what is the volume occupied by the settled particles, that is required to pre-load the formula in "variable command". Can voronoi/atom be used ? or what will output will voronoi/atom give me to help calculate packing fraction ? please help.

regards,

you asked for a way to find out the maximum z coordinate of the particles. The commands I've mentioned above can be used to get that.

Thanks for replying man, any ways, I found another method to circumvent the problem. I ran my simulation in "ovito" and froze it at a time when the particles settled down and took note of the corresponding file at that time. I went to that file and found out the maximum "Z- coordinate" using matlab, and then proceeded ahead. But also, I read your commands in documentation, I could not figure out how to use them to find "z coordinate" after particles settled down. Please can you tell me how they are used ?

regards,

compute maxz all reduce max z
The value is then accessible using c_maxz.

Thank you man, It is working, but I need to use reduce/region instead of just "region", to serve my purpose, any ways, thanks a lot.

Hey people, I want to know how to specify a constant temperature to a specific imported geometry , so that it conducts the heat to the particles that are in contact with it. Also I tried tried the following command " pair_style gran model hertz tangential history heating_tangential_history on heating_normal_hertz on " adding extra inputs of " heating_tangential_history " and " heating_normal_hertz " assuming that it would invoke the surface conduction properties for the particles, which is required for temperature update of the particles. But I'm getting error as

ERROR: Unknown argument or wrong keyword order: 'heating_tangential_history' (../pair_gran_base.h:120)

So, how do I get the particles to conduct heat and change its temperature too, simultaneously , because of the hot geometry (floor) beneath them ?? Please help.

regards,

No offense, but you can't just make up new command options and expect LIGGGHTS to interpret them.
Study the heatTransfer tutorials and the corresponding documentation:
http://www.cfdem.com/media/DEM/docu/fix_heat_gran_conduction.html

None taken, thanks I'll look into it.