Noise-sustained structure in Taylor-Couette flow with through flow

We report experimental and theoretical results for the absolute and convective instability boundaries in Taylor-Couette flow with imposed axial flow as a function of the axial Reynolds number. Experiment and theory agree quantitatively. In the downstream region of a large-aspect-ratio system, noise-sustained structures of traveling vortices exist in much of the convectively unstable regime. These structures have a nearly time-independent amplitude, but a noisy phase. The phase noise ceases abruptly upon crossing the absolute instability boundary.