Separated flow past a rotating circular cylinder has been investigated by the flow visualization. Experiments were conducted to investigate the cases in which the velocity ratio of the cylinder's skin to the uniform stream was varied from 0 to 6 at a Reynolds-number of 200. Wake patterns are divided into three main categories in terms of the velocity ratio; (i) regular vortex street, (ii) sheet-like structure, and (iii) turbulent vortex. Visual observations indicate that there exist transitional patterns between one flow regime and the other.
