A Retrospective on Modulated Wavy Vortex Flow. Michael Gorman, Univ. of Houston and Harry Swinney, Univ. of Texas at Austin. Circular Couette flow with the outer cylinder fixed undergoes three bifurcations before the onset of turbulence. The initial steady, azimuthal flow undergoes a bifurcation to Taylor vortex flow in which N vortices form along the axis of rotation. At a second critical value of the rotation rate, these flat vortices become unstable to the formation of M waves traveling around the annulus. Our experiments followed on the work of Gollub and Swinney, who observed a second characteristic frequency before the onset of turbulence. We found that the second frequency corresponded to the independent modulation in the shape of each wavy vortex subject to the condition that the phase, φ, between successive modulations equals K*2π/M. We present video (recently converted from 16 mm film and never before presented publically) of three MWVF states. Circular Couette flow is an example of a fluid system which becomes turbulent more gradually than most other fluid flows.