[lammps-users] fix viscous

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1

Dear LAMMPS users,

I would like to use fix viscous in a granular simulation. However I'm not sure about gamma units.

Documentation says:
gamma is specified in force/velocity units (SI [kg/s]).

With gamma = kT / m / D and D = kT / (6 pi eta d)
gamma = 6 pi eta d / m in 1/time units (SI [1/s]).
The Stokes drag force would be F = - 6 pi eta d / m * v.

I presume the definition gamma = kT / m / D is wrong and should read
gamma = kT / D.

/TW

2

You're right - the code for fix viscous was corrent
but the doc page was incorrect. It should be gamma = kT/D.
I confused this due to the similarity with fix langevin
where a mass is added to the damping factor to get force.

I changed the doc page to clarify this.

Thanks,
Steve