  We study the dynamics of a doubly quantized vortex (DQV), created by
releasing a ring-shaped Bose-Einstein condensate with quantized circulation
into harmonic potential traps. It is shown that a DQV can be generated and
exists stably in the middle of the ring-shaped condensate with the initial
circulation $s = 2$ after released into the rotationally symmetric trap
potential. For an asymmetric trap with a small degree of anisotropy the DQV
initially splits into two singly quantized vortices and revives again but
eventually evolves into two unit vortices due to the dynamic instability. For
the degree of anisotropy above a critical value, the DQV is extremely unstably
and decays rapidly into two singlet vortices. The geometry-dependent lifetime
of the DQV and vortex-induced excitations are also discussed intensively.
