  We study the behavior of four types of vorticities in non-central Au+Au
collisions at energies $\sqrt{S_{NN}}$ = 5--200 GeV using a microscopic
transport model PACIAE. The results show that the vorticities decay faster at
lower energy and smaller impact parameter. The non-monotonic dependence of the
initial vorticities on the collision energies is reconfirmed and the turning
point is 10-15 GeV for different vorticities. The global $\Lambda$ polarization
at energies $\sqrt{S_{NN}}$ = 7.7--200 GeV is reproduced by introducing an
energy density freeze-out criterion.
