The vortex flow is one of the fundamental types of fluid and gas motion,it is characterized by the localization of vorticity in bounded regions of a space,beyond which the vorticity is absent or rapidly falls to zero.Concentrated vortices are often observed in nature,exemplified by atmospheric cyclones,whirlwinds and tornados,oceanic vortices,whirlpools on a water surface,and ring vortices caused by explosive outburst of volcanoes.In technical devices concentrated vortices form when flow separates from sharp edges of flying vehicles and ships,airplane wings,etc.One remarkable and frequent type of concentrated vortices is a vortex ring which constitutes a vortex tube closed into a toroidal ring moving in a surrounding fluid like an isolated body which is out of contact with solid boundaries of the flow region,if such boundaries exist.The formation and motion of vortex rings are an important part of the dynamics of a continuum medium and have been studied for more than a century.These investigations promoted elucidation of many general mechanisms of vortex motions,and recently provided a basis for developing high efficiency operating procedures[1].