compute the L2 Distance between two fields
-sx --shiftx shift by Lx/2 -sz --shiftz shift by Lz/2 <flowfield> (trailing arg 2) input field #1 <flowfield> (trailing arg 1) input field #2
L2Dist u.ff v.ff
Note: the -sx and -sz options apply shifts by Lx/2 and Lz/2 to one of the fields prior to computation of the norm. This is helpful for my research but might not be of interest to others.