git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@5530 f3b2605a-c512-4ea7-a41b-209d697bcdaa

doc/velocity.html

@@ -24,6 +24,7 @@
     seed = random # seed (positive integer)
   <I>set</I> args = vx vy vz
     vx,vy,vz = velocity value or NULL (velocity units)
+    any of vx,vy,vz van be a variable (see below)
   <I>scale</I> arg = temp
     temp = temperature value (temperature units)
   <I>ramp</I> args = vdim vlo vhi dim clo chi
@@ -52,7 +53,7 @@
 <P><B>Examples:</B>
 </P>
 <PRE>velocity all create 300.0 4928459 rot yes dist gaussian
-velocity border set NULL 4.0 3.0 sum yes units box
+velocity border set NULL 4.0 v_vz sum yes units box
 velocity flow scale 300.0
 velocity flow ramp vx 0.0 5.0 y 5 25 temp mytemp
 velocity all zero linear 
@@ -69,7 +70,20 @@ number generator with the specified seed as the specified temperature.
 </P>
 <P>The <I>set</I> style sets the velocities of all atoms in the group to the
 specified values.  If any component is specified as NULL, then it is
-not set.
+not set.  Any of the vx,vy,vz velocity components can be specified as
+an equal-style or atom-style <A HREF = "variable.html">variable</A>.  If the value
+is a variable, it should be specified as v_name, where name is the
+variable name.  In this case, the variable will be evaluated, and its
+value used to determine the velocity component.
+</P>
+<P>Equal-style variables can specify formulas with various mathematical
+functions, and include <A HREF = "thermo_style.html">thermo_style</A> command
+keywords for the simulation box parameters or other parameters.
+</P>
+<P>Atom-style variables can specify the same formulas as equal-style
+variables but can also include per-atom values, such as atom
+coordinates.  Thus it is easy to specify a spatially-dependent
+velocity field.
 </P>
 <P>The <I>scale</I> style computes the current temperature of the group of
 atoms and then rescales the velocities to the specified temperature.