Fig. (7) (1) Spatial power spectra of v fluctuations at z = 1.3, T = 3.5 and Re = 510, when a strong disturbance is continuatively introduced at Re ~ 255. (2) Frequency spectra of the wavenumber 32 component measured for T = 2.5 ~ 3.5. (3) Frequency spectra of the wavenumber 64 component.