Vortex shedding around a half-cylinder. Here the arrow layer is produced from Gerris (gfs) output with the command

vfplot -v -w4i -m4/4/0.5 -s0.0002 -i200/5 \
    -P0.4 -f255 -l0/1i -d bvk.dom \
    -o vfplot.eps -F gfs frame-2.0.gfs

For the background, the vorticity is extracted from the gfs file and formed into a GMT grd file

gfs2xyz2D -s Vorticity frame-2.0.gfs | \
  xyz2grd -R-0.5/1.5/-0.5/0.5 -Gvort.grd -F -I256+/128+

then the background is plotted with a GMT script which also overlays the arrow layer.

RNG="-R-0.3/0.7/-0.3/0.3"
DIM="4i/2.4i"
PRJ="-JX$DIM"
COM="+defaults $PRJ $RNG"

GRDC="vort.grd"
GRDF="vort-fine.grd"
VEPS="vfplot.eps"

grdsample $GRDC -G$GRDF $RNG -N512/512 -Q

grdimage   $GRDF $COM -C$CPT        -K >  $EPS
grdcontour $GRDF $COM -C$CPT -A- -O -K >> $EPS
psimage    $VEPS -W$DIM          -O    >> $EPS

Download the plot as pdf, or the domain and gfs (0.4 MB) data files.