  The dynamical development of collective flow is studied in a (3+1)D fluid
dynamical model, with globally symmetric, peripheral initial conditions, which
take into account the shear flow caused by the forward motion on the projectile
side and the backward motion on the target side. While at $\sqrt{s_{NN}} =
2.76A$\,TeV semi-peripheral Pb+Pb collisions the earlier predicted rotation
effect is visible, at more peripheral collisions, with high resolution and low
numerical viscosity the initial development of a Kelvin-Helmholtz instability
is observed, which alters the flow pattern considerably. This effect provides a
precision tool for studying the low viscosity of Quark-gluon Plasma.
