[gmx-users] Constant-velocity pulling

[Sajjad Kavyani]

Dear experts,
I'm trying to do a constant-velocity pulling of water particles through a
tube.
First, I did the process with a constant force constant successfully but
now for the constant velocity, I do not get how to choose parameters in the
.mdp file!.
I read the umbrella sampling tutorial, manual and actually did a search in
the mailing list mails but some how I'm nervous to choose between!

This is the the pull code for the constant force pulling:
;;; Pull code:
pull                          = constant-force
pull-geometry = direction-periodic
pull-ngroups = 1
pull_group1_name   = W
pull-coord1-vec  = 0 0 1
pull-coord1-k = 50
pull-coord1-groups = 1

1. Could you please tell me how to modify the above code for the constant
velocity (for example v=v0) pulling and explain to me the parameters ?
2. And what is exactly the "pull-coord1-groups" parameter and how to choose
the correct value? If I have tow group to pull (one with constant-force and
another with constant-veocity  )?