Keywords: 
• 螺旋波 /
• 失稳 /
• 时空混沌 /
• 缺陷湍流

Abstract: Using a reaction-diffusion system as an example,we introduce the basic properties of spiral waves in excitable or oscillatory media,and discuss different routes that lead from an ordered spiral state to a chaotic state.First we present some basic properties of spiral dynamic,such as its emergence,development,and transition.Then we discuss our recent experimental results on the spiral instabilities of the Belosov-Zhabotinsky reaction in a quasi-two-dimensional reaction-diffusion system.Two routes leading to spatio-temporal turbulence have been observed in the experiments.Both of them can be characterized by defect-mediated-turbulence.The first instability is due to the Eckhaus instability,which generates defects at a distance from the spiral center because of its“convective”nature.The second instability creates defects in the spiral center.The mechanism of the instability is linked to the Doppler effect,when a Hopf bifurcation contributes to the spiral core,making the latter meandering.