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.
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