Dynamics of blinking vortices.

We investigate the dynamics of N moving point vortices, whose vorticity changes periodically between a finite value and zero. The dynamics of such blinking vortices is chaotic, but the degree of chaoticity, expressed in terms of finite size Lyapunov exponents, decreases monotonically with time. In contrast to traditional point vortices, the average diameter of the blinking vortex system increases in time. The average size follows a subdiffusive power law scaling approximately t;{sigma} , with sigma<12 . This expanding vortex system provides a flow which is in between closed and open flows. The advection dynamics generated by the blinking vortices is also studied, and leads to dye distribution patterns which are much more realistic than those of the classical point vortex problems, and can be characterized by a dimension less than 2.