Dear Steve And Georg,
There are some examples in examples/USER/sph directory. Among them there is an example with name water_collapse. The unit that have been used in this example is “lj”. When change this unit to another unit such as “si” or “cgs” without change other values such as mass , timestep, density, etc. all results are the same. I think it is a bug. Please clear me.
Thanks a lot
Yasti
water_collapse.lmp (2.34 KB)
data.initial (3.38 MB)
Dear Yasti,
the SPH implementation does not work with actual physical units. It is only assumed that the input script uses a consistent set of units.
No conversion factors to switch between different unit systems are applied anywhere in the USER-SPH package.
Mit freundlichen Grüßen / With best regards,
Georg Ganzenmüller
So Georg’s answer is the good news. You can use any
self-consistent units in LAMMPS. LJ, cgs, si are all self-consistent
units.
The bad news is that unless the SPH package uses the
standard conversion factors that the rest of LAMMPS
uses, you cannot use it with non-consistent units.
E.g. real, metal, or anything else. Those factors
are all 1.0 for self-consistent units, but are not
for other units.
So I’d consider that a potential bug of the SPH package.
Georg - is that documented somewhere or checked
for within SPH to throw an error if the user chooses
invalid units?
Steve
Dear Steve,
no check for that is implemented as of now.
I should add a check to both USER-SPH and USER-SMD.
Best wishes, Georg