Dear Axel and other LAMMPS users,
I want to put “meff” (effective mass) variable defined in “pair_gran_hooke_history.cpp” (granular package) into “fix_ave_spatial” for output/dump file. As I am not advanced programmer in C++ so I need help. Please can anybody help me in this connection? I want to show the relationship between effective mass versus filling mass for janssen analysis as a function of height.
Thanks in advance.
Sincerely yours,
Ram
Since meff is a function of the 2 masses of a pair of particles,
I don't understand what it would mean in a dump or fix ave/spatial
context, since those work on single particles.
Steve
Dear Axel and LAMMPS users,
I thought in C++ it was written for apparent mass. Actually I want to pull out apparent mass(Mapp) which is weight felt at the bottom of silo as the function of filling mass. Apparent mass is only the fraction of filling mass. I think the equation is written somewhere in sources but I couldnt dig it out. Please guide me.
Thanks…
Ram
I don't think LAMMPS computes anything like this. If you specify
the eq for "apparent mass", then I can tell you if it would be
easy for you to write a compute to calculate.
Steve
I don't think LAMMPS computes anything like this. If you specify
the eq for "apparent mass", then I can tell you if it would be
easy for you to write a compute to calculate.
i am by no means an expert on simulating granular materials,
so please take the following with a large grain(!) of salt:
to me this sounds very much like the intent is to
compute the total force in some layer at the bottom
of a container in direction of gravity.
if this guess is correct the term "mass" is used with some
liberties and actually means "weight", and that in turn
is linked to the force through gravity.
just a thought,
axel.
Respected Steve,
Thank you. I found the way of calculating apparent mass. But I dont know if this is right. We can calculate this in input script by defining variables. But there is no output for stress vector (rr) as like (zz). Can I use
stress(rr) =sqrt(stress(xx)^2+stress(yy)^2) for calculating stress along radius? stress(rr) is required for the calculation of apperent mass. Here are all formula for calculating apprent mass:
Mapp=Msat*(1-exp(-Mfill/Msat))+Qexp(-Mfill/Msat), [ means multiplication]
where Msat=rhoSR/2muK and Mfill=rhoSh,
where S=PI*R^2, R is radius of cylinder used, rho is density of grain, mu coeff of constant of wall, h is height of cylinder, Q=stress(zz) at the top of cylinder and
K=stress(rr)/stress(zz)
Stress(zz) can be calculated by LAMMPS but stress(rr) not.
Am I right?
Sincerely yours,
Ram
If by Srr, Sxx, Syy you mean per-atom quantities, then
LAMMPS can accumulate Sxx and Syy and you can define
an atom-style variable that computes Srr according to
your formula below, which will be evaluated when thermo
output (or some other output) is done.
If instead, you need to accumulate, Srr on a pairwise basis,
then you would have to modify the pair_granular routines
to do this.
Steve