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A new spin on bluff body wake transitions

Prof. Kerry Hourigan

Faculty of Engineering, Monash University

Airfoil geometries are used for aircraft wings (and seacraft sails) because they provide high lift, low drag and little vortex shedding, leading to stable motion. A non-rotating cylinder has zero mean lift, high drag and can suffer severe vortex-induced vibrations – however, increasing the spin rate of a cylinder leads to high lift, low drag, with vortex shedding disappearing; the Magnus effect can be used to advantage in Flettner rotor sails and wings. The 2d and 3d wake transitions for a cylinder in a uniform flow as its spin rate is increased have been investigated both numerical and experimentally. It is found that a remarkably rich array of two- and three-dimensional transitions occurs in the wake for low Reynolds number. Surprisingly, very large flow-induced vibrations can occur for an elastically mounted spinning cylinder, even when the vortex shedding is suppressed.