Hit Reload if
the Animation doesn't start. Hit Stop to Freeze the Animation.
This animation of pictures
of a vortex (diameter 0.1m) separated with a 0.25s time step illustrates
The 3 first pictures from t=0.005s
to t=0.05s show a fast growing vortex has the instability is building up.
At the same time the peek velocity is climbing too (up to 1,39 m/s at t=0.05s).
Then the vortex is not gaining
amplitude anymore. As the vortex is spiraling the velocity vectors form
an almost steady circular pattern causing the "cats eyes". The peek velocity
is falling towards 1 m/s.