抄録
The Karman wake remains a classical paradigmatic system for the study of fluid dynamic systems. It exhibits, at once, the simple periodic oscillator form that complex flow around a bluff body can take; while at the same time exploding into complex dynamics when the stable oscillator is perturbed by external forcing. It is not surprising, then, that in practical applications, e.g. VIV and control, empirical relations are still used when estimation of VIV amplitudes are needed for design purposes. This paper, and in particular, the talk itself, investigates the influence and contribution of nonlinear dynamics to our understanding of the Karman wake dynamics and vortex-structure interaction in general. Much work has been done, 'proving' that the Karman wake behaves often like a low dimensional nonlinear system. The van der Poly oscillator exhibits many of the characteristics of the Karman wake-at least qualitatively. Lock-in, quasi-periodicity and chaos have been found. Yet, while qualitative agreement has been shown, quantitative comparison remains to be presented. The greatest challenge appears to be lack of a simple but realistic model for the Karman wake-if such a model exists. It is proposed that the full potential of recent developments recent in nonlinear dynamics is yet to be exploited.
