fix smd/integrate_ulsph command


fix ID group-ID smd/integrate_ulsph keyword
  • ID, group-ID are documented in fix command
  • smd/integrate_ulsph = style name of this fix command
  • zero or more keyword/value pairs may be appended

keyword = adjust_radius or limit_velocity

adjust_radius values = adjust_radius_factor min_nn max_nn
adjust_radius_factor = factor which scale the smooth/kernel radius min_nn = minimum number of neighbors max_nn = maximum number of neighbors
limit_velocity values = max_velocity
max_velocity = maximum allowed velocity.


fix 1 all smd/integrate_ulsph adjust_radius 1.02 25 50

fix 1 all smd/integrate_ulsph limit_velocity 1000


The fix performs explicit time integration for particles which interact with the updated Lagrangian SPH pair style. See this PDF guide to using Smooth Mach Dynamics in LAMMPS.

The adjust_radius keyword activates dynamic adjustment of the per-particle SPH smoothing kernel radius such that the number of neighbors per particles remains within the interval min_nn to max_nn. The parameter adjust_radius_factor determines the amount of adjustment per timestep. Typical values are *adjust_radius_factor*=1.02, *min_nn*=15, and *max_nn*=20.

The limit_velocity keyword will control the velocity, scaling the norm of the velocity vector to max_vel in case it exceeds this velocity limit.

Restart, fix_modify, output, run start/stop, minimize info:

Currently, no part of USER-SMD supports restarting nor minimization. This fix has no outputs.


This fix is part of the USER-SMD package. It is only enabled if LAMMPS was built with that package. See the Making LAMMPS section for more info.