  The dynamics of the coherent structures in jets generated by nozzles of
different shapes is analyzed through DNS at $Re_{D_e}=565$, by considering
circular, square, fractal and star-like nozzles. The jets generated from
orifices with corners, undergone a rotation proportional to the corner angular
width: ${\theta}_{rotation}={\theta}_{corner}/2$. The velocity at which this
rotation occurs is also affected by the angle of the corners, being faster for
fractal and star-like nozzles which have small ${\theta}_{corner}$. Therefore
it has been found that the velocity of the rotation is associated with enhanced
spreading and entraining characteristics. The jet evolution and its rotation
are dictated by the vorticity field and, in particular, by the positive and
negative ${\omega}_x$ layers generated at each corner. The comparison between
the fractal and the star-like jets at this Re, suggested that the effect of the
smaller scales generated by the fractal nozzle does not play a role in the
development of the jet, that evolves as the star-like one.
