I'm carrying out a simple indenter simulation, in which a cylinder is slowly pushed vertically into a box of particles.
Currently, I use the following to get the forces on the indenter:
...
compute fc all wall/gran/local id pos force
...
dump forcedump all local $e post/dump*.forcedata c_fc[1] c_fc[2] c_fc[3] c_fc[4] c_fc[5] c_fc[6] c_fc[7] c_fc[8] c_fc[9] c_fc[10] c_fc[11] c_fc[12]
When I visualise the forces (having created paraview compatible vtk from the above), it seems to be in the right place, and behave correctly.
However I'm wary here for a couple of reasons. Firstly, I'm also using an STL to act as the container for the particles. Is it getting incorporated into this? As I say, the force vector seems to be in the right place, and individual forces only show at the indenter not at the box walls, so my inclination is not.
Secondly, I can't for the life of me figure out what the 12 variables are I'm outputting. As best I can gather, based on old information and documents I used, c_fc[1] to 3 are the x,y,z coordinates of the particle in contact, and 10,11,12 are the fx fy fz of that particle. it seems that 9 is the particle ID, but I can't work out what the other columns are.
If there's a more sensible way of calculating the force on the indenter, I'd love to hear suggestions.
Thanks.
kunzhang | Wed, 07/23/2014 - 17:58
You could also dump your stl
You could also dump your stl as vtk file and check it in the paraview. The command is:
dump dumpstl all stl 100 post/dump*.stl
So you could make sure if it is get incorported.
I am not quiet sure about the second questions.
Kun
pfalkingham | Fri, 07/25/2014 - 10:31
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Thanks. Yeah, I'm already dumping the stls as VTKs. They are in the simulation, but it's whether it's incorporated into the force output. it doesn't look like the box is (which is good), but then I'm not sure why it isn't. i.e. i'm not clear how I've managed to output the forces on one stl and not the other.
ckloss | Sat, 07/26/2014 - 21:36
Hi,
Hi,
compute wall/gran/local can only process data from a fix wall/gran command of mesh type
>>Secondly, I can't for the life of me figure out what the 12 variables are I'm outputting
This is documented in the doc for the "compute wall/gran/local " command.
Best
Christoph
pfalkingham | Wed, 07/30/2014 - 15:14
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Thanks Christoph,
At the moment I have two fix wall/gran commands:
#----------WALLS----------##Sets up the physical walls
fix outerBox all mesh/surface file openbox.stl type 1
fix boxwalls all wall/gran model hertz tangential history mesh n_meshes 1 meshes outerBox
#----------SETS UP THE INDENTER----------#
fix indenter all mesh/surface file Indenter.stl type 1 move 0 0 -0.03
fix indent1 all wall/gran model hertz tangential history mesh n_meshes 1 meshes indenter
#----------COMPUTATION----------#
# sets up what will be computed
compute rke all erotate/sphere
compute mudisp all displace/atom
compute fc all wall/gran/local id pos force
#----------DUMP FILES----------#
dump dmp all custom $e post/dump*.bin id x y z fx fy fz f_myorig[3]
dump dumpstl all mesh/vtk $e post/indent*.vtk id indenter
dump forcedump all local $e post/dump*.forcedata c_fc[1] c_fc[2] c_fc[3] c_fc[4] c_fc[5] c_fc[6] c_fc[7] c_fc[8] c_fc[9] c_fc[10] c_fc[11] c_fc[12]
#----------RUN SPECIFICS----------#
fix moveIndenter all move/mesh mesh indenter linear 0 0 -0.0001
Yet it only seems to be relaying information about the indenter-particle contacts... is that right? Should I make that into a single wall/gran command that refers to both meshes?
Also, the order of columns in my forcedata.dump appears to be pos_1 ... pos_6, id_1 ... id_3, fx, fy, fz... which is the order they are listed on the manual page for compute wall/gran/local, but not the order I listed them (which was id, pos, force). Again, is that right?
Thanks,
Peter.
ckloss | Mon, 08/25/2014 - 23:14
Hi Peter,
Hi Peter,
the compute pair/gran command will only attach to one fix wall/gran of mesh type.
I.e. you would have to lump all walls into one fix wall/gran of mesh type.
I think the order you list should be correct
Cheers
Chris