I was reading about http://en.wikipedia.org/wiki/Aeolian_harp" [Broken]. It is explained that "the harp is driven by von Karman vortex street effect" So I read about http://en.wikipedia.org/wiki/Von_Karman_vortex_street" [Broken]. I also read a few other sources on von Karman vortex street effect. It is known for the steady flow around a smooth circular cylinder that: for Re < 5 no separation of the flow occurs; for 5 < Re < 40 a fixed pair of symmetric vortices exists in the flow; for 40 < Re < 200 laminar vortex street exists in the flow; My question is why the flow changes its regime? I. e. why the vortices appears for Re > 5 and why the vortices begin to shed (and what force makes them to so) for Re > 40 and what force made them stay (not shed) for Re < 40? Why do they shed in that ("chess-board", "lamp-post", etc) particular order? And has any research been done on the topic at all? (I mean exactly why the regime changes. I understand that for each separate regime a lot of research has been done) Can anyone please explain or point me to such an explanation? Thank you!