halting a rotating cylinder

A rotating cylinder in an infinite fluid generates a stable rotational flow, but if the cylinder is suddenly halted, then an unstable flow is induced. Paul Cardinaels has kindly provided the Gerris simulation data for such a flow illustrating the vortex generation and shedding.

The original gfs file is converted to the more convenient GMT grd format using the gfs2xyz2D utility. The resulting u.grd and u.grd files are used to generate the arrows layer with the command

vfplot -v -w8i -m5/5/-0.4 -s1e-4 -i300/5 \
       -P0.1m -f100 -l0/1in --cache 256 \
       --aspect 3.0 --glyph triangle \
       -o vfplot.eps u.grd v.grd

The arrows layer is then composited using GMT, a grd file of vorticity, vort.grd, and a colour scale vort.cpt derived from the diverging Andy_GIlmore_2 scheme.

Download the plot as pdf.

mvpoly plot
Unstable flow induced by the halting of a rotating cylinder