SPARTA WWW Site - SPARTA Documentation - SPARTA Commands

fix move/surf command


fix ID move/surf Nevery Nlarge args ... 


fix 1 move/surf 100 1000 all trans 1 0 0
fix 1 move/surf 100 10000 all rotate 360 0 0 1 5 5 0
fix 1 move/surf 100 50000 object2 rotate 360 0 0 1 5 5 0 


This command performs on-the-fly movement of a selected set of surface elements via one of several styles. Surface element moves can also be performed before or between simulations by using the move_surf command.

Moving surfaces during a simulation run can be useful if you want to to track transient changes in a flow while some attribute of the surface elements change, e.g. the separation between two spheres.

All of the command arguments which appear after Nfreq, which determine which surface elements move and how they move, are exactly the same as for the move_surf command. See its doc page for details.

Nevery specifies how often surface elements are moved incrementally along the path towards their final position. The current timestep must be a multiple of Nevery.

Nlarge must be a multiple of Nevery and specifies how long it will take the surface elements to move to their final position.

Thus if Nlarge = 100*Nevery, each surface elements will move 1/100 of its total distance every Nevery steps.

The same rules that the move_surf command follows for particle deletion after surface elements move, are followed by this command as well. The criteria are applied after every incremental move. This is to prevent particles from ending up inside surface objects.

Restart, output info:

No information about this fix is written to binary restart files. No global or per-particle or per-grid quantities are stored by this fix for access by various output commands.


An error will be generated if any surface element vertex is moved outside the simulation box.

Related commands:

read_surf, move_surf, remove_surf

Default: none