V = multivortex(NFIELD, NSIZE, NUMVORTEX) returns NFIELD vector fields 
of size NSIZExNSIZE points (1 point = 1 mm), containing a set of 
NUMVORTEX random Burgers vortices (vortices with Gaussian vorticity and 
divergence profiles). The location, core size, vorticity and divergence 
of each vortex is random. V is a standard PIVMat structure array, which 
can be displayed using showf. 
 
Default parameters are NFIELD=1, NSIZE=128, NUMVORTEX=8. 
 
Note: Vortex centers are distrubuted in an area larger than the field 
of interest, in order to ensure statistical homogeneity. As a 
consequence, NUMVORTEX is the *average* number of vortex per field. 
 
V = multivortex(..., 'Property1','Property2') specifies additional 
vortex properties: 
  'asym'   all vortices have positive vorticity 
  '2d'     impose zero divergence 
 

 
  showf(multivortex(1,256,6,'asym'),'rot'); 
 
  v = addnoisef(multivortex(10,128,5,'2d')); 
  showf(filterf(v),'rot','contourf',12); 
 

showf, vortex, addnoisef. 
Published output in the Help browser 
   showdemo multivortex